I tried to create interest in a user provided, forum maintained data base of carrier service sites on a different website. That is the best way to know what your service might be like. The carriers' coverage maps are almost useless (VZW is totally useless). I suggest the minimum content for a given cellular service structure would be: Latitude, Longitude, and a list of all carriers at this location. Note that I am using "cellular" generically; some people get upset because they hold that "cellular" should only be used for the 850 MHz band, "PCS" is the 1900 MHz band, etc. Life is too short for this errant pedantry!
My personally gathered data base (incomplete because of paranoid carriers and tower owners)for my tri-state corner of PA, NY, and NJ has more detail but the files are large.
Let me know if this idea can get any traction on MobileTechReview. I'm new here so if I have broken any taboos, let me know that also.