Pittsburgh Coal Company had a mine near the Hills station until 1953, Mine No. 4. The mine and the PRR-Montour interchange was also at this same location. The links below provide more details and photos.
It is hard to determine the exact location of each spot of interest, but, to me at least, it looks like the PRR had to go on to the interchange tracks to gain access to the mine. The Hills passenger station was on the Chartiers branch proper. From the station, employees could walk to the mine on the east.