I don't know how many changes have been made to police operations since this document was written, but there is an overview of police operations that includes a description of eight patrol zones here:
http://www.paed.uscourts.gov/documents/opinions/98d0636p.pdf
Just search the document for "zone".
The patrol zones are basically built around the Market Frankford El and the Broad Street Line.
I don't think the zone 8 exists anymore. As the previous poster mentioned, I think Zone 1 also covers suburban areas for regional rail as well as part of the MFL. If Zone 8 no longer exists, I'm not sure what officers would cover incidents to the north (i.e. NE Philly and Bucks).
I never see SEPTA police at the Norristown Transportation Center any more. In fact, SEPTA currently has an agreement with the Montco Sheriff's office that has deputies making rounds through the NTC during the weekdays. I'll often see a sheriff's patrol car parked there in the afternoon rush time.