In the case of the Lehigh Valley, it was a Penn Central property, owned to the tune of 80% or 90%, I forget the exact figure, but never merged into the system - the PRR took control about 1962 and tried to pawn it off as part of the prep for the PC merger, but neither C&O or N&W wanted it.
The CNJ was similarly aligned with the B&O until about 1972 when the USRA plans began to take shape; by then they gave up on their tracks in PA which became LV operated by default.
All of these companies gave up the rail assets and properties in the final system plan, to Conrail, and the Penn Central and even the LV continued to exist for some time after to dispose of the property not included in the Conrail system, be it through leasing for operation, sale, or scrap/demolition. Penn Central itself became an insurance company that has since changed names a couple times, possibly at least one via another merger.