I have also looked into this. There are repeaters all over and they are to be linked to an OpenSky TG but I'm not sure how they get enabled (both repeater side and patch) and/or who controls the links.
I have been monitoring the U-TAC's in Delaware county for 1.5 years and am yet to hear any activity.
I do hear occasional traffic on the 8TAC channels and I believe it is coming out of PA (Possibly Bethlehem or Allentown since they are both on 800).
I forgot to mention that I have heard, on several occasions, traffic control operations on 8TAC channels. I can only assume this is from a PennDOT crew that wandered off the state's simplex channel and onto the 8TAC channel during their roadwork. The two state simplex channels (analog and P25 version) are in the same "bank" as the 8TAC's.
The 8TAC repeaters that you know of, are they analog PL 156.7 as suggested in the NIFOG or did the Commonwealth do their own thing ? Also is there a list with locations like in the UHF and VHF overlays ? The map you provided is a tad small, it appears that there maybe a site close to me but I can't tell for sure