It does if they find the bomb belt, now doesn't it?
All he's got to do is put it on.
They'd have a far better success ratio by simply searching anyone who looks like they could be a Muslim, and decent folks wouldn't need to be suborned into this charade.
If there were a practical benefit to the bag searches then it would be another story. But if you think that such searches will do a thing to keep a bomb off the subway, then you don't understand the NYC subway system. There are way too many entry points and way too many station and way too many passengers.