
Continuity mistake: In the car chase scene, Mason is driving the stolen Hummer and he hits a meter maid truck sending it flying into a telephone pole and blowing it up. They slow down the film a little here and show us this hit from several different angles including from above. When they slow down the film you can see that the Hummer is turned sideways in the impact but in the next frame it drives off as if it had just tapped the meter truck and not slammed into it as shown.
Chosen answer: Alcatraz is small enough and out in the middle of the bay that any lookout in a high point could see and hear a chopper, no matter where it approached from. The idea of the decoys was to split any enemy fire received. The whole insertion of SEALS was absurd, in a real situation like that, the SEALS would have been inserted by submarine or used dive motors to pull themselves to the island.
Grumpy Scot