Verizon Wireless press release that provides some insight into the cost and size of a typical Mobile Telephone Switching Office (MTSO)
Mike Sandman's Central Office (CO) database - search for the telephone switching offices (COs for land-lines and MTSOs for mobile telephones) in a given area (these are the central "hubs" that route calls and control towers)
Telephone Prefix Locator at TheDirectory.org - Find out where telephone exchanges (prefixes) are located (using this database with Mike Sandman's Central Office database above gives you an idea of how large of an area a given CO or MTSO covers)
AntennaSearch.com - locate existing and planned cell phone towers and antennas throughout the US, based on proximity to a specific address
Article about number portability on Wikipedia - this explains how a call is routed when a number has been ported from one carrier to another
