So the proper way then would be....
You completely missed the point of a417's post. By "the proper way", he was referring to the fire company reaching out to DCNR/SRND to find out how they might be able to better communicate between agencies.
It's unlikely that the state is going to build out 800 MHz infrastructure in Centre County just so a volunteer fire company can talk to DCNR. Besides which, the XTS would be useless as the STARNet P25 system does not allow FDMA talkgroups. The system also uses radio authentication, which requires the APX subscribers to have the AES algorithm.
If they really need to directly communicate with DCNR that badly, the FD can simply obtain some cheap VHF analog radios that they can use on one of many good old fashioned simplex VHF nationwide interop channels.
Final point...the DCNR fire ops talkgroups are encrypted, and so it's pretty unlikely that they're going to permit anyone outside the agency to get their key loaded into radios they have no control over.
Oh and also, consider the source asking the question lol.