As part of their bid for Super Bowl XLVIII, the Jets and Giants proposed the AFC team use the Giants facility and the NFC team use the Jets facility. The reasons were clear: The Jets were not thrilled at the prospect of the Patriots descending upon Florham Park and the Giants were not necessarily excited about the Cowboys, Redskins or Eagles checking into their facility for the week in East Rutherford.
The NFL has final say on who practices where and the suggestions by the Giants and Jets were rejected. It’s standard Super Bowl practice that when an AFC team is hosting the game, the AFC team practices at their facility. And the NFC team practices at the NFC facility when they are hosting. So the NFL is just following protocol.