I know they can use "Time of Arrival" positioning, but it's not very
accurate unless all the receivers (minimum of three) are synchronised to a
single reference such as the GPS clock.
All cell towers are.
Unfortunately, triangulation doesn't work very well because in most
places, your phone only sees one or two antennas at a time and if
there are more, it's usually in an area with reflections. Go indoors
and all bets are off. But, what is more effective, especially with
smart phones, is to use the WiFi capability of the phone to improve
the accuracy of the position.
Consider that nearly all WiFi hot spots are mapped.
SPS (Schnozz Positioning System)