[f1shy]

In 2009 I worked with a triangulation system in a dense populated area. The precision of location was comparable in average to GPS (meaning sometimes better) when indoors, it was orders of magnitude better as GPS. That was 3G, some yeras ago… I assume today is much better, as the density of cells increased

[DeepSeaTortoise]

I'd be very interested in more info, but am going to doubt this for now. Usually just the intra-day deformations of the terrain between the towers through hydrological activity should far exceed what GNSS can achieve.

It is just VERY VERY hard to beat the predictability of orbits.