The line that you refer to is indeed owned presently by the B&P (owned by the Genessee & Wyoming RR, from NY, a shortline agglomerator). This line was originally built by the Allegheny Valley RR, and is known as "the Low Grade Line". It went from Redbank to Driftwood at a very favorable grade of less than 1%. AVRR was bought out by the PRR in 1910, line was built in 1871 to 1873/4.
This line was originally concieved to provide a low grade alternative to the PRR grade over the Alleghenies. For many years, this line did provide an alternative, but it was much longer than Altoona/Cresson/Johnstown, so it wasn't used for this purpose all that much. It did provide lots of coal sourced along the branch, and coal drags were common up until very recently. The end from DuBois to Driftwood still sees some coal traffic.
Just to the east of this track, along PA 255. is the old Buffalo and Susquehanna RR ROW. This road paralelled the AVRR from Dubois to Driftwood, hauling coal from Indiana County, PA (Sagamore) to points north, and was abandoned around 1950 after a major flood.
Dan