In the penultimate scene just before Meredith gets on the L train, the overhead sign says Trains To O'hare Airport, but this station is Western on the Brown Line. Trains do not run to O'hare on the Brown Line, rather the Blue Line which also has two other stations of the same name.
When Gary and Meredith are on the rooftop and she falls over the edge, Gary tries to pull her back up, and the mic is visible above.