This was supposedly in the _charter_ of the department of homeland security. It was supposed to be the controller of all intelligence (all agencies to dump their databases together), from all the spy agencies to prevent the intentional use-case of employing jumbo jet planes as weapons of mass destruction. And forcing all cell phones of every design every where to have GPS. Seems a little bit slow.
Cell phones need some kind of accurate-enough (GPS is arguably overkill) self-locating ability, because the encryption properties of the modulation make passive transmitter location and ranging determination difficult: they need to know when to switch between cell towers (ENodeB).
Wiener functions are cool, and the RADAR applications were top secret during WW II.
Aside from that ENodeB uses GPS for timing. At the base station. In a way that does not require your phone to _also_ have GPS.