All perfect praise be to Allah
Firstly, i should say(again) that this is more the matter of TAQWA(fear of Allah) than the matter of pure halal and haram. Because if I(personally) fear that something contains haram ingredients in it in any quantity, i will avoid that. Because if i eat that food knowing that some haram thing MIGHT be in it, i can be held accountable for eating haraam in aakhirah, because indirectly i know that this might be haram.
Now, coming to the actual question, their might be a slight favor we can get in this matter, otherwise most of the ulema agree that the food which is contaminated, or mixed up with haraam somehow is also haram. Because haraam is haraam, it is in more quantity or less, haram will remain haram.
Now read below hadees,
Hadîth related in Sahîh al-Bukhârî and Sahîh Muslim.
Abû Tha`labah al-Khushanî said to Allah’s Messenger (peace be upon
him): "We come from a land populated by the People of the Scripture.
Can we eat from their dishes?
The Prophet (peace be upon him) replied: "Do not eat from them unless
you do not find anything else to eat from. In that case, wash them and
eat from them."
This means we should be cautious about it because caution in these matters means “guarding oneself against falling into sin.” prophet ﷺ also said so because their was chance of haraam in their food. Though we are not certain, but we should avoid and not take chances.
The Prophet (peace and blessings of Allaah be upon him) said: “Every
body that is nourished with haraam things, the Fire is more befitting
for it.” Narrated by al-Tabaraani
I am sure no one is willing to take chance on this.
But keep in mind, this is for the contamination which is most probable, but if the restaurant takes care of halal food separately with care, than that's different. And if the haram and halal are being cooked on same place in same dishes without proper washing than that's different and should be avoided.
Let me quote a beautiful hadees in the end:
On the authority Abi Ab’dillahi al-Nu’man ibn Basheer (ra) who said: I
heard the Messenger of Allah (peace be upon him) say: “That which is
lawful(halal) is clear and that which is unlawful(haraam) is clear and between the
two of them are doubtful [or ambiguous] matters about which not many
people are knowledgeable. Thus, he who avoids these doubtful matters
certainly clears himself in regard to his religion and his honor. But
he who falls into the doubtful matters falls into that which is
unlawful like the shepherd who pastures around a sanctuary, all but
grazing therein. Verily every king has a sanctuary and Allah’s
sanctuary is His prohibition. In the body there is a morsel of flesh
which, if it be sound, all the body is sound and which, if it be
diseased, all the body is diseased. This part of the body is the
[Related by al-Bukhari and Muslim]
Allah knows best