More to the point, how do members of the constellation calculate and correct their position? I seem to recall ground stations being used as a reference.
You don't actually triangulate using signals sent to and from the satellites, or "track" them. All the SVs do is transmit, at a lowly 50W, a time signal, an almanac and ephemeris data. In other words, all the SVs do is say, "At this time on this date I will be at this point in the sky and this high above the spheroid." The receiver does all the work, using trilateration, to determine your position from ranges and bearings; essentially a GPS satellite is a transmitter that sends out a big-ass look-up table of numbers - which is why you want a nice spread of seven to nine SVs around you to get a decently accurate fix.
It's a myth that "GPS can be used to track you." GPS receivers do just that - receive. The transmitter in your 'phone, however, can be used by software to broadcast your position once it has got it from the built in GPS receiver.
And here endeth the lesson.