While I can't really help you with the tower locations, just remember that a tower will only carry traffic if a unit is affiliated on that tower on that specific talkgroup. Most radios lay around on dispatch, so dispatch for whatever agency is most likely to be carried by most towers in the area. If units switch to a Tac or Ops channel, probably the only tower(s) that will carry the traffic is right around where the field units are located and the tower dispatch is hooked to. As far as affiliation, most county talkgroups allow roaming one county outside the "home" county, so as far as the radio is concerned its going to hook to the strongest signal and ignore county lines. If an event happens in the western side of the county, there may be a tower in the east side of the county that doesn't even carry the Tac or Ops channel. Basically is what I'm getting at is that it is all hit and miss to what talkgroups will be over what tower at a certain time. Not really a problem for the users of the radio because our radios affiliate on the channel we want to hear and the radio makes sure we hear it, but a problem for scanner users.