I've used it a couple of times - it was set up in the weeks leading to the Super Bowl. It really is a sad excuse for a cell phone lot - basically a sectioned off area of a vacant parking lot. No amenities, just a place to park and wait.

The cell phone lot is on the south end of parking lot P1, near the last stop of the AirTrain. The entrance to the lot is off of Basilone Road and Brewster Road, south of the passenger terminal complex.