District 4 was doing radio tests a while back. Usually, before the roll out in a given area, DCNR personnel can be heard doing radio tests using portables on the Global Tac channels. These same radios float around the state (same RIDS) in advance of the roll outs. They were recently heard testing in Districts 17 and 18.
If I had to guess, I would say District 4 is on the air now or will be soon. I'm not familiar with their daily operations, but it seems most of the state forest lands for that district are in the Laurel Highlands area. So, they would probably mostly affiliate with tower sites out that way. DCNR has clear talkgroups and encrypted talkgroups. They do not appear to use selectable encryption. If they want to go secure, they change to a secure channel, same as PGC.