I've never seen anything to indicate there is a "canonical" list of amsar. Part of the problem is that the history of the conquest wasn't written at the time it occurred but rather compiled from oral histories several centuries later. The people who preserved these memories and the compilers who eventually wrote them down often had their own priorities at stake. For example, you might claim that your hometown accepted Islam willingly, whereas you might claim that a rival town needed to be conquered by force and occupied. That's not to say people were necessarily manipulating the historical record, but oral history often simplifies events and interprets them according to the contemporary political and cultural situation, rather that according to the terms used at the time in question.

If you're curious about the mechanics of garrison towns, check out Hugh Kennedy's The Great Arab Conquests (2007). It's got great detail on the nuts and bolts, but like most of these histories, he necessarily relies on al-Tabari—a brilliant and eminent scholar of the 10th century, but by no means what we today consider a primary source for the 7th century. For what I think is a more compelling narrative of the conquests, check out Robert Hoyland's In God’s Path (2015). Both of them are well indexed and have flush bibliographies, so if there's anything like an amsar list out there, you'll find it in Kennedy or Hoyland.