A lot depends on what you know about the others, and also - it was the FT bubble but not the cash bubble. If it were the cash bubble, I'd say fold since you come away with plenty of chips. In a $1 MTT, I think it's fair odds that you are ahead even against the shove, although I do see that you'd be worried someone hit 2 pair, it's hard to believe someone calls off the 2.5bb preflop with Q6, Q4 or 64 when they're not in the blinds. Tough one, but I think I would have called.