Waw i did not hear about the mmpool drama, so sad to hear about it, but just to make things clear, the pool's server and private key was stolen, this could happen to any pool that isn't fully secured, so as far as the current topic is concerned, a miner can't change the pool's btc address after solving a block, the funds will arrive at the pool's address, then it is a matter of how secured the pool's keys are.