Among the osol (the sources) of fiqh (see also in What are basic (osol al fiqh) differences & similarities between the 4 (existing) Legal Sunni Schools: Hanafi, Hanbali, Maliki, & Shafi'i? Charts?) one of the most discussed and disputed is that one of 'amal ahl al-Madinah عمل أهل المدينة which was considered as a major source by imam Malik after the Qur'an and sunnah, while having a higher level than hadith al-Ahaad if this was not a hadith describing a "practice" of the Prophet () (A hadith where only a saying not a doing of the Prophet was transmitted).
Imam al-Laith ibn Sa'ad discussed it with Malik during his life time while imam a-Shafi'i discussed it in numerous books where he even pointed at deviations of Malik from what we could call Ijma' of the scholars of al-Madina, the later was considered by ibn Taymiyyah as close to truth (Is it true that the Prophet Muhammad foretold the birth of Malik ibn Anas??)!
My question is how exactly is 'amal ahl al-Madina defined and adopted in the maliki madhhab?
I strongly assume that practices of people of Medina after the death of imam Malik wouldn't fall into this category, so is there a temporal limitation for what practices and during what times fall into this category?
And as I've read that scholars of the madhhab had some differences about this source of Jurisprudence it would be great if it is possible to point at some of these differences (see also Difference between Ijma' on transmission and Ijma' on opinion)