Hello,
the most action is Amtrak on 161.295. Various PL's for the area but just run it CSQ. This repeater has a very wide area of coverage.
The regional rail line SEPTA uses 502.6375R. Monitor without a PL and you will also hear PPD's J Band where most all major crimes are broadcast.
Amtrak has a helo that patrols the main lines N/S of Philadelphia. They use 155.475 to communicate with local agencies.
PPD is all digital so just look at the RR DB.
Dave