The idea is not to recreate the coins. The idea is to allow MtGox to make a transaction from a wallet that supposedly they have lost the private key to, this is a wallet that has hundreds of thousands of BTC in it so not many people could be claiming ownership. The way security work with BTC is that to make a transaction you must have your private key sign the transaction to prove you are the owner of the wallet. If the transaction is not correctly signed it is rejected as a fraudulent transaction. The idea is to let MtGox make a fraudulent transaction from a wallet they have lost access to. They would convince 51% of the miners to accept the unsigned or incorrectly signed transaction as being legit and the transfer would go through. There is no duping of coins as the original wallet that is inaccessible would be drained of coins.
I understand that, but it's a chicken and egg problem. How can MtGox prove they own the wallet they're trying to make a fraudulent transaction from if they don't hold the associated private key?
