Useful maybe but expensive (at least in the older networks). Handset reported cell-tower signal strength information (what you need to triangulate) was only acc

Useful maybe but expensive (at least in the older networks). Handset reported cell-tower signal strength information (what you need to triangulate) was only accessible to non-core parts of the network to reduce data load on regional links. Typically you can find out which areas have spotty coverage by looking at the dropped call and load stats of base stations (which use directional antennas), looking at osm maps of roads and developments, collecting complaints, as well as occasionally calling out and taking field measurements.