I think you misunderstand the idea of a networked system. Every site on the RACOM net is interconnected, so a Polk County Deputy could be in Council Bluffs, and his radio will still hear Polk Co Ops. If any radio affiliates with a talkgroup, it will automatically bring any traffic on that talkgroup to the site. So if an officer turned to a talkgroup used by Council Bluffs, it would come in on the site he was on.
Think of it like cell phone roaming, no matter where you go, your call stays connected, but not every site in the network has your call, just your tower and the tower of the person you are calling. But in this case, there can be 16383 callers on the same line, each with their own tower if the system was that large.