This was discussed in the gaming forum. Supposedly it is not (yet if it is threaded, OS X will allow it to, but it isnt specifically programmed to).
The consensus is though, that the game is not held back by the CPU, it is very GPU intensive, so the CPU wont be a bottleneck, and SMP support wont make that much improvement.
pop over to the gaming forum, theres discussion about it there.
revs