All 4 zones have solar sites in them. I'm not 100% sure on how they work but, in my experience, they vary from having 1 to 3 frequencies. Big Moose is the site I use the most. Big Moose A is a full-time patch to Zone 3A. Big Moose B is used more as a talk around channel for wardens, forest rangers, and park rangers and can only be used between solar sites. I have not heard the 3rd frequency used. I would assume the zone 4 solar sites are used in a similar manner. You have to be within range of a solar site to hear the traffic on them unless it's on the frequency that is a full-time patch to Zone 4A. In the case of Big Moose, Bangor RCC monitors both A and B solar "channels." Someone with more understanding of these solar sites can hopefully add more detail but they seem to work very well.
In terms of scanning I believe you would set them up as one frequency trunk systems but I have only used them in my radios and just programmed them as conventional P25 personalities.
