From BOF..
“A movie production asked Pittsburgh Public Schools to arrange for some of the district's closed school buildings to be made available to location scouts from a film company. Obviously that filmed turned out to be THE DARK KNIGHT RISES. Tours of four closed elementary schools were given, and of the four, I've enclosed photos of the one building in which they were 'very interested.' The building’s interiors seemed to be their priority.”
Jett over at BOF reckons since it's possibly the interiors of these buildings that they are interested in, if it may be this movie's version of The Old Post Office from the Chicago shoot of The Dark Knight. This was the hub for much of the interior shooting for that movie.