Suppose it depends if cell IDs and locations are available, and whether that data can be scraped and used for a map, or if it's even legal or not.
In the United Kingdom, OFCOM publishes a Google Map with all UK cell locations, including carriers, IDs, types, output powers etc.
Sitefinder Mobile Phone Base Station Database
This data is probably Crown Copyright, and most likely can't legally be used for other purposes, like an app or something.