“Gotten Away”? Yes, they likely would have been caught... BUT - I doubt it would have been all that difficult to drop a backpack and walk away, dial a cell # and boom. Literally less than 1 minute operation.
Yes - there is security and surveillance - but when one only needs seconds... The authorities are minutes away.
We learned from the last attempt that Times Square is under constant surveillance and police are always on scene. NYPD is much bigger and is on a different level when it comes to counter-terror.