You could see some Prime in the lesser cuts like brisket and chuck, CAB steaks will almost always just be Choice. CAB is restricted to maturity A and modest to moderate marbling. You won't see small marbling or maturity B like you will with just a Choice label, so it is the better portion of the Choice rating.
As far as brisket, there is little to no wholesale premium for anything above Select grade. Select will have less fat and higher yield so restaurants will have a higher food cost with Choice or Prime even if they do not pay a per pound premium.
Many packers will not isolate and sell brisket, chuck, or round as Prime because there is a very limited market and it is not worth the effort to segregate and merchandise it as Prime.
Also, there is plenty of Choice beef selling for > $11/pound online. Go to some of the online steak places and try to find the word 'Prime'.