Let me give a little insight into how the overall system is supposed to go over the next 5-10 years. Eventually there will be an 700/800 system throughout the entire MTA operating area. Starting with equipment located at each train station, and then expanding out. MTA also wants to lease out their system and towers any agency/ business who wants to pay for it to cover the cost of the build out. (I have had numerous requests about it from agencies all over the Tri State area) That is what I believe is one of the problems with them getting permissions for their towers in some towns and villages other than the usual BS of NIMBY. It changes their status from a state agency to a business, and there is already a court precedent on this when NYSP and Westchester County wanted to rent out space on their tower in New Rochelle. I suspect the new site for Peekskill will be at a new tower at the train station since we have no tower there now.
NYSP was supposed to build out a statewide OpenSky system, but we all know how that went. NYSP was about to lose all their 800 allocations from not building out on time from the local co-ordinator and in a pre-emtive strike they gave them to MTA. Now MTA has lots more money from DHS than NYSP had to build a system. They recently spent nearly a million $ on mobile and portable radios(VHF/800). They intend to keep the VHF for direct contact with the Rail operations, and the 700/800 will be for PD operations, and yes unfortunatly will eventually be (E).
To jump start the system in CT, they worked a MOU with CSP to use their system while enhancing it with additional MTA sites. I suspect it's possible that might also happen on LI.
On the Long Island I suspect the build out would be the same, first in train stations and along the ROW. Nassau Med would be my first choice for a site covering the South shore, but isn't very good toward the North. LIRR had a large amount of equipment up there until the 90's.
You are right on target about the politics involved.
As far as District dispatching, they can get very busy at times and I have been told to wait before I could do maintence on a site because X was going on. Also MTA is now dispatching the FD/EMS Brigades located in each of the yards, and that results in more radio traffic. So i do see them splitting the desks up more.