Installed the game on 'Snow Leopard' 10.6 with nary a problem under CrossOver Games 10.0.1. Under DirectX 9.0c and with Motion Blur off, game ran ok.
Same problem as R6 Vegas 2 though: mouse gets 'stuck' or 'hits an invisible wall' if you rotate the view to be friendly to someone. Impedes gameplay.
Running 'regedit' from 'Run Command' menu and then adding a 'DirectInput' item to Hkey_current_user/software/wine, plus making a 'MouseWarpOverrun' item in that (see R6 Vegas 2) and assigning a 'force_edge' value to that fixed the problem.
Other than that, doesn't seem to have any problems (sound takes a few seconds to come up though). Runs well on my 2,4 GHz C2Duo Mac Mini 2010. This was on Rainbow 6 Vegas 1.06.215 (from the R6 Vegas compilation dvd) (DMCA).
Other than the program occasionally crashing, only real problem seems to be getting shot rather a lot by sneaky bastards behind every other corner...