this is btc from mybitcoin
It could be, but several of the people who have sent BTC to addresses for their mybitcoin accounts have noted that the funds have not been moved from those addresses.
That's cause when the site went down, so did the bot that used to immediately send the coins to another account from the receiving account, mix them all up with a ton of small trades, and god knows what else. If you look at your blockexplorer history for your mybitcoin receiving address you will see what I am talking about.
I don't have any mybitcoin transactions to look at unfortunately (fortunately?).