Yeah, that shows they had it in 2011, but doesn't prove they have squat today.
It does prove that the BTC is owned by mtgox and the BTC is STILL there.... assuming the IRC is not faked. which means the question is:
Does mtgox have the private key for these addresses?
I would assume these wallets are being encrypted with different keys. If you do this, I think you're not stupid enough to put the encryption keys in the same place. This makes me to believe access is possible but unavailable. Maybe he put them in safes in banks but cannot access them.
Otherwise, fuck yea... 200k coins lost forever if he lost the keys.