The system will only pass TG'S from one site to another if a radio affiliates to it. There are no 'automatic patches' on the standard patrol channels, but it is very often that almost all Troop C patrol TG'S come across Troop B, and I'm sure it's similar for Troop C.
Don't forget that talkgroups can be set as requested on sites. This is often to ensure that scan properly works. What this means is that if no radios are affiliated to a particular talkgroup and the site has capacity at the time you hit PTT then the traffic will go out over that site regardless of affiliation status.
They may have these talkgroups set to overlap on the larger simulcast cells. For the smaller sites they may not be set this way to ensure that capacity is available only for those channels affiliated.
On top of this there are security profiles on systems which say is the radio allowed on this site, on this talkgroup, etc. There are the same for talkgroups as well.
If you us a subscriber on a talkgroup and it affiliates to a site where the talkgroup is not allowed it will go back to site scan to find a site where it is authorized. If it can't find a site where it is allowed and the talkgroup chosen is allowed the radio will show "Out of Range" even though you are in range of a site on the system which theoretically can carry the talkgroup but is not allowed to.
