With the exception of UPMC sites in Pgh (not including a few outside of the city), LECOM rotates in all of those systems. In fact they send a decent amount to AHN and Conemaugh as year-long regional sites for core rotations. Let me know if you want more info. I know that doesn't really answer your question, but just extra info.
From what I've heard, PCOM rotates at some Pgh UPMC sites (like Shadyside, McKeesport, etc.). I doubt that includes Presby, but I'm not sure. They don't send kids to AHN for core rotations as far as I know, and I have no idea about Conemaugh. That said, as a 4th year, you could apply for electives at any of those locations.
Either way, I wouldn't be too worried residency wise. UPMC affiliates (not Presby), AHN, and Conemaugh take DOs from PCOM and LECOM all the time. As long as you make it a point to do auditions and electives at those sites, and do well, it's very reasonable to expect to come back to Pgh for residency.
Hopefully someone at PCOM can comment on how the residency selection process goes.