Might be a trick question I'm falling into, but I think the Big Blind should have folded. Unless there is a split pot, two of the three players will be eliminated/severely crippled almost certainly ensuring an "in the money finish".
I actually think flat calling with aces here is somewhat marginal also (but I'm not a sit n go expert either). I'd rather pick up the extra chips than take the added risk of having one or two callers behind. Also, if you reraised with aces in this spot you may still get action from medium pocket pairs who think you have AK (or possibly a smaller pair)and are willing to gamble. If any overcards hit to their pocket pair on the flop, they can fold thus saving chips they would have otherwise called with.
I'l be interested to hear the sit n go experts opinion though because I'm primarily a cash game player
Jason
