How many scholars hold this opinion , and what are they basing it on?
My impression is that the Shafis hold this opinion and they base it on the literal meaning of أوتوا الكتاب and أوتوا الكتاب من قبلكم in 5:5 as other people who adopted Judaism and Christianity were not given the Scriptures by Allah.
Zuhaili in الفقه الإسلامي وأدلته seems to say that he doesn't know their evidence, and has cited that the Sahabah ate the food and married the women of the people of the book without investigating their lineage.
Does the person who is from the people of the book have to
slaughter the animals in a special way?
They must fulfill all conditions of ذكاة as there is no evidence to suggest that they get waived just because the slaughterer is not a Muslim. I am only aware of a difference of opinion on pronouncing the name of Allah.
Jassas in أحكام القرآن has presented the argument that the Quran has commanded us to not eat what is dedicated to other than Allah وما أهل به لغير الله and Jesus is other than Allah and there is no concession or exception in the Quran to allow his name to be pronounced. Similarly there is no evidence that 5:5 is independent and has abrogated other verses like 6:121 or 5:3 and so it is obligatory on us to act on them all simultaneously since it is possible to do so.
What are the conditions for meat to be halal if the
animal was slaughtered by the people of the book?
Below is my personal translation of a relevant section from Jaziri's book الفقه على المذاهب الأربعة which details the conditions according to the four schools of thought of the Ahlus Sunnah. Note that the translation is paraphrased, and may contain mistakes and omissions.
المالكية - قالوا: يحل أكل ذبيحة الكتابي، أما صيده فإنه لا يباح إذا مات الصيد من جرحه أو أصابه إصابة أنفذت مقتله. أما إذا أصابه إصابة جرحته ولم تنفذ مقتله ثم أدرك حياً وذكي فإنه يؤكل ولو بذكاة كتابي، وبعضهم يقول: يحل صيد الكتابي كذبحه سواء أماته أولم يمته
وإنما تحل ذبيحة الكتابي بشروط ثلاثة،
Maliki: They say: The meat slaughtered by the People of the Book is halal ... [omitted rulings on their hunted meat] ... There are three conditions for their slaughtered meat to be halal:
الشرط الأول: أن لا يهل بها لغير الله فإذا أهل بها لغير الله بأن ذكر اسم معبود من دون الله كالصليب والصنم وعيسى وجعل ذلك محللاً كاسم الله أو تبرك بذكره كما يتبرك بذكر الإله فإنها لا تؤكل، سواء ذبحها قرباناً للآلهة أو ذبحها ليأكلها، أما إذا ذكر اسم الله عليها
وقصد إهداء ثوابها للصنم كما يذبح بعض المسلمين للأولياء فإنها تؤكل مع الكراهة. وإذا ذبحها ولم يذكر عليها اسم الله ولا غيره فإنها تؤكل بدون كراهة، لأن التسمية ليست شرطاً في الكتابي. وبعضهم يقول: إن الذي يحرم أكله من ذبيحة الكتابي هوما ذبح قرباناً للآلهة،
وهذا ليس من طعامهم المباح لنا بالآية الكريمة: {وطعام الذين أوتوا الكتاب حل لكم} لأنهم لا يأكلونه بل يتركونه لآلهتهم، أما الذي يذبحونه ليأكلوا منه فإنه يحل لنا أكله ولوذكر عليه اسم غير الله تعالى ولكن مع الكراهة.
The first condition: The name of someone other than Allah should not have been pronounced. Pronouncing the name of someone other than Allah means that they say the name of someone other than Allah - for example the cross, or an idol, or Jesus - with the belief that taking that name makes the slaughtered meat halal in the same way that saying Allah's name makes it halal . Also it is the same if the name is taken to receive blessing. In this case the meat will not be eaten, and it doesn't matter if the animal was slaughtered as a sacrifice to the false deity or slaughtered for normal food.
However if they pronounce Allah's name and their intention was that the reward would go to some false deity, similar to how some Muslims sacrifice to bring reward to saints, then it may be eaten but is makruh. Similarly if neither Allah's name was pronounced nor the name of someone else, then it may be eaten
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الشرط الثاني: أن يذبح الكتابي ما يملكه لنفسه. فإذا ذبح حيواناً يمكله مسلم فإنه وإن كان يحل لكن مع الكراهة، على الراجح
The second condition: What is slaughtered by a person from the People of the Book must be their personal property. If they slaughter an animal which is owned by another Muslim then it is halal but makruh.
الشرط الثالث: أن لا يذبح ما ثبت تحريمه عليه في شريعتنا، فلا يحل أكل ذي ظفر ذبحه اليهودي كالأبل والبط والأوز والزرافة ونحوها من كل ما ليس بمنفرج الأصابع لأنهم يحرمون أكله، وقد أخبر القرآن بأن الله حرمه عليهم
أما الذي لم يثبت تحريمه عليهم في شريعتنا كالحمام والدجاج ونحوهما فإنه يحل لنا أكله إذا ذبحوه، وإذا أخبروا بأن هذا الحيوان محرم عليهم ولم يخبرنا شرعنا بتحريمه عليهم فإنه يحل مع الكراهة، فإذا كان الكتابي يستحل أكل الميتة وذبح حيواناً فإنه يحل أكله إذا كان
بحضرة مسلم عارف بأحكام الذبح، أما إذا ذبحه وحده فإنه لا يحل أكله،
The third condition: That what has been slaughtered by them should not be something which was haram for them. For example an animal with uncloven hoofs which has been slaughtered by a Jew, like the camel, duck, goose, giraffe and any others who do not have split hoofs and are haram for them to eat, because Allah has informed us in the Quran that He forbade them from these [6:146].
And something which is not proven to have been forbidden to them, such as pigeons or chicken etc. then these are halal and may be eaten when slaughtered by the people of the book.
And if there is something which they claim is forbidden in their religion, but we don't have evidence in our shariah for it being forbidden or permitted to them, then it is halal but makruh.
If a person from the people of the book believes that it is permitted to eat carrion, then whatever he slaughters is only halal if a Muslim, knowledgeable in commandments of slaughter, is present when he slaughters it. And if such a person from the people of the book slaughters something while alone then it is not halal to eat.
ويستثنى من حل ذبيحه الكتابي المستكملة لشروط الأضحية فإنه يشترط فيها أن يكون الذابح مسلماً تصح منه القربة، فإن استناب عنه رجلاً لا يعرفه ثم تبين له أنه غير مسلم فإنها لا تجزئه، والشرط أن يتولى المسلم الذبح، أما السلخ والقطع ونحوهما فإنه لا يشترط له ذلك
The slaughtered meat of a person from the People of the Book is permitted to eat, but they can not slaughter an animal in place of a Muslim for ritual sacrifice (udhiyah). And if a person gets his sacrifice slaughtered by another and then it is discovered that the slaughterer was not a Muslim then it is not valid, because it is a condition of sacrifice that if someone else is appointed to slaughter the sacrificial animal then he should be a Muslim. However this condition does not exist for skinning the animal or butchering the meat.
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الحنفية - قالوا: يشترط لحل ذبيحة الكتابي يهودياً أو نصرانياً أن لا يهل بها لغير الله بأن يذكر عليها اسم المسيح أو الصليب أو العزيز أو نحو ذلك، فإذا حضره المسلم وقت الذبح وسمع منه ذكر المسيح وحده أو ذكره مع اسم الله فإنه يحرم عليه أن يأكل منها، وإذا لم يسمع
منه شيئاً فإنه يحل له الأكل على تقدير أن الكتابي ذكر اسم الله في سره تحسيناً للظن له، أما إذا لم يحضره ولم يسمع منه شيئاً؛ فإن التحقيق أن ذبيحته تحل، سواء كان يقول الله ثالث ثلاثة أولا، يعتقد أن العزيز ابن الله أولا. ولكن يستحسن عدم الأكل لغير ضرورة. ولا فرق
في النصراني بين أن يكون عربياً أو تغلبياً أو إفرنجياً أو أرمينياً أو صابئياً إذا كان يقر بعيسى عليه السلام، ولا فرق في اليهودي بين أن يكون سامرياً أو غيره. ويكره أكل ما يذبحونه لكنائسهم.
Hanafi: They say: The condition on which the slaughtered meat of a person from the People of the Book: a Jew or a Christian, is that the name of someone other than Allah should not have been pronounced on it. For example the name of the Messiah, or the cross, or Uzair etc.
If a Muslim was present at the time of the slaughter, and he heard the name of Messiah alone, or the name of Messiah along-with the name of Allah being uttered then it is haram for him to eat it. And if he heard nothing then it will be halal as the benefit of doubt will be given that Allah's name was whispered. And if a Muslim was neither present nor heard anything, then too it will be considered halal ... Though it is preferable that it is not eaten without need.
And it makes no difference whether such a Christian is an Arab or of the Banu Tughlab or a Frank or Armenian or Sabean who believes in Jesus. Similarly there is no difference if he is a Jew or a Samaritan etc. And it is makruh to eat whatever has been slaughtered for a church.
الشافعية - قالوا: ذبيحة أهل الكتاب حلال، سواء ذكروا اسم الله عليها أولا بشرط أن لا يذكروا عليها اسم غير الله كاسم الصليب أو المسيح أو العزيز أو غير ذلك فإنها لا تحل حينئذ ويحرم أكل ما ذبح لكنائسهم
Shafi: They say the slaughtered meat of the People of the Book is halal, whether or not Allah's name has been pronounced on it or not. However the condition of it being halal is that the name of someone other than Allah should not have been pronounced on it, for example the Cross, Messiah, Uzair or someone else. In that case it would not be halal. Similarly that which is slaughtered for a church is haram to eat.
الحنابلة - قالوا: يشترط في حل ذبيحة الكتابي أن يذكر اسم الله تعالى عليها كالمسلم، فإذا تعمد ترك التسمية أو ذكر اسم غير الله تعالى كالمسيح فإن ذبيحته لا تؤكل، وإذا لم يعلم أنه سمى أولا فإن ذبيحته تحل، ذبح، لعيده أولكنيسته فإن ذبحها مسلم وذكر اسم الله عليها فإنها
تحل مع الكراهة، وكذا إن ذبحها كتابي وذكر اسم الله، أما إذا ذكر غيره أو ترك التسمية عمداً فإنها لا تحل
Hanbali: They say: The condition for the slaughtered of the People of the book being halal is that the name of Allah is pronounced on it, similar to the way of the Muslims. If the name of Allah is omitted intentionally or the name of someone other than Allah is mentioned then it should not be eaten. If it is not known whether Allah's name was pronounced or not, then it is halal. Whatever is slaughtered for their festivals or events at churches and has been slaughtered by a Muslim, and Allah's name has been pronounced on it, is halal but makruh. The same applies when slaughtered by one from the People of the Book when Allah's name has been pronounced. If someone else's name is pronounced or Allah's name is not pronounced intentionally, then it is not halal.