So, maybe this is too technical but may I ask why a state system couldn't handle all that traffic? Wouldn't they just have to add more towers and frequencies for that site?
Thanks.
(and sorry I am trying to learn more about trunking systems, as my county is moving from VHF to UHF trunking system soon)
There are several factors in play here. First, as you indicate, they would need to add many towers and frequencies to properly cover the city fully. Second, many new talkgroups would need to be added to the state system. The third factor, which is probably the major sticking point, is cost and control.
If the city owned the system, they have full control and can easily add talkgroups, radios, and additional agencies as desired. By joining the statewide system, they must work with them to add these as they're needed. If they owned the system and had an emergency need for new talkgroups (say for a special event) they could simply ask their radio folks to create them and get them added to the desired radios. If they were on the statewide system it may take too long to get this accomplished (as well as being charged for doing so).
The statewide system charges a monthly fee for each radio on the system, so there's an ongoing cost. If the city owned their own system, they pay upfront for the radios (possibly using grant money) and have only minimal monthly costs (for maint, repairs, etc.). Using the statewide system, there may be a time when they would need to give up some of their radios due to a budget shortfall (to save the monthly cost) where if they owned their own system this wouldn't be on the table (although the radios may not get repaired or replaced if broken due to the lack of funds).