If they can produce logs of every single transaction they've ever done, including moving coins to the cold wallet, then anyone who wants to could examine the blockchain and match up transaction times and addresses with MtGox's claims. If they tried to claim ownership of someone else's wallet, that person could easily disprove their claim by signing an address with the corresponding private key.
No matter how thorough the audit, it wouldn't be enough to convince every last user of the system. But it only has to convince enough people that the few remaining holdouts are forced to either follow suit or create a fork.
No matter how thorough the audit, it wouldn't be enough to convince every last user of the system. But it only has to convince enough people that the few remaining holdouts are forced to either follow suit or create a fork.