You don't mention what model scanner you're using, but obviously it is one that support P25 digital trunked radio systems. Severalyears after Palmetto 800 rebanded, in fact about 18 months or so ago, Palmetto 800 upgraded from a Astro 25 mixed mode (analog and digital talkgroups) system to a full P25 system. Whereas the older system, with its older style 3600bps control channel, required a special bandplan table to be set for the new rebanding frequencies, the newer P25 9600bps control channels carry the system bandplan as part of its data stream. P25-capable scanners decode that table information from the control channel and use it calculate voice frequencies. No special "rebanding tables" are required.
The answer to your second question is more complicated. At any given time, a particular trunked radio site will carry only the talkgroups that have radios affililated to that site tuned to that talkgroup. So, fore example, as long as a DCSO deputy's radio is affiliated with the Darlington Co site and is tuned to their dispatch talkgroup, that talkgroup will be carried on that site. If a DCSO deputy's radio affiliates with a nearby site, say the Lee County site, and tunes to the DCSO talkgroup, and assuming that talkgroup is allowed by the system programming to be carried on that site, that talkgroup will be heard on the Lee County site. As soon as that last radio tuned to that talkgroup deaffiliates from the Lee County site, it will no longer be heard on that site.
In the upstate, I regularly hear medical helicopters from around the state on the local sites. Their talkgroups are allowed to roam to all sites on the system. Likewise, SCHP talkgroups can be heard far away on a regular basis. They often patch talkgroups for neighboring troops together so the dispatcher can work all troops on one channel. So you'll hear troopers from more distant troops on "local" troop talkgroups.
Hope that helps.
