The Pennsy Schuylkill division was built later, I think in the 1860s but I'm not sure. That's why it's located on higher ground between Manayunk and Norristown, out of the flood plain.
I don't have information about the situation at Douglassville.
Pennsylvania RR Schuylkill Division was built in the 1880s.
When the Feds sued for Superfund cleanup money, they used a very wide net and made mistakes. The Reading Company could have been a suspected customer of Douglasville Disposal, perhaps by trying to sell them a gallon of used locomotive oil.