The 700MHz PSIC overlay sites were built out mostly by federal interoperability grants that each state gets for such projects. There are more sites planned for addition in the same manner to expand the footprint.
The sites are connected back to the Lake core via a network that each county already had a connection to. This solution was much more cost effective, by a large order of magntiude over interconnecting every other system with each other via ISSI.
The PSIC talkgroups themselves are valid system-wide and are extremely useful for events that can span multiple geographical areas. Think pursuit on Turnpike, VIP movement via motorcade, funeral procession that traverses many counties, SAR involving many different agencies on disparate radio system technologies. FHP, FWC and most local agencies that are within coverage of the sites have control stations that they can patch to their native subscribers for interop between users without the officer trying to find a resource ten zones deep when they are focusing on the task at hand.
