This is the same collector that is found in Mac OS X Leopard 10.5.3 (the collector was not updated as a part of 10.5.4 or 10.5.5).
The garbage collector is not limited to Objective-C. It is actually a fairly generic scanning, conservative, generational, multi-threaded, language agnostic, collector. The implementation has certainly been tested and optimized with Mac OS X based applications.
Notably, MacRuby uses AutoZone to offer a common GC implementation across object graphs that span Ruby and Objective-C.