Websites for both Genesee & Wyoming RR/Buffalo & Pittsburgh and Carload Express/Allegheny Valley have maps that indicate Allison Park, PA is the location for interchange. An unofficial railfan website for the Allegheny Valley shows Bakerstown, PA as the interchange location. All I can make out from Bing maps is single track at both locations, which would make it difficult to run engines around a train.
I have posted videos on Youtube of AVR-4 passing through Panther Hollow in Schenley Park, Pittsburgh around 8 PM. Power has been 3 engines and a pretty sizeable train. Glenwood Yard is close enough to pick up talk on a scanner. https://www.youtube.com/watch?v=i6MKbPL ... C&index=50
While visiting someone in Renfrew, just south of Butler, I heard horns from a train which I assume was the BPRR heading south and later returning north. Time for one trip was around 7 PM on a Friday. A couple weeks later, I sat in Mars and Valencia, hoping to see the BPRR without luck.