Doubtful, for tanks, I'd say the only limit for them should be numbers... say 2-3 per team... but not just the CATTB, the limit could be for all tanks; so there can be variety in PVP battles.
There shouldn't be a limit like this for PVE games thou. The limits in PVE should be tank class based, like since there can only be 1 arty, it should also be only be 1 AFV, 1 TD, and/or 1 LT as well. With no limits on the number of MBT's since the more the better (I love getting games where everyone's in a mbt).