I have no info about the UT's use of GPS, but given that you can basically construct a practically-unbreakable geofence around the fact that the UT can only phy

I have no info about the UT's use of GPS, but given that you can basically construct a practically-unbreakable geofence around the fact that the UT can only physically see a specific set of satellite(s) at any particular point in time (and space), and you get this property for free given the UT's purpose, I can't imagine that not being leveraged in the design.