When the D&H was awarded trackage right on Conrail, the historic Columbia & Port Deposit branch was part of the route to Washington, DC. When the PV&T took over the D&H, those trackage rights (and most of the overhead wire; Conrail had clipped the wires at Perryville, but hadn’t yet sent out the salvers to scrap the rest of the wire) followed along. This gave an approximately 150 mile section of track under the wire (C&PD/Port Road from Harrisburg to Perryville, NE Corridor to Washington), which became an opportunity to expand the electrification, and so Conrail sold all of the Port Road’s overhead (and a small handful of E44’s) to the newly purchased D&H, which started to plan a wholescale electrification of D&H south from Albany to the coast (these plans took A While to implement, because Conrail had positively no interest in allowing their tenant railroad’s overhead north of Harrisburg.)
In the mid 1990s, the D&H rerouted their Philadelpia traffic over the C&PD, the (now D&H owned) Atglen & Susquehanna & Philadelphia & Thorndale, and the Main Line instead of along the old Alphabet Route through Reading. They also arranged haulage rights along the NE Corridor from Philadelpha to Perryville (there was little enough traffic coming out of New Jersey to afford Amtrak usage fees on the super-busy Philadelphia/New York City segment) as a secondary line, and when NS & CSX bought and dismembered Conrail in 1999, the D&H was given permission to finally electrify between Harrisburg & Sunbury, thus tying the C&PD into the rest of the D&H’s electrification.
The new trackage rights was not the only concession that NS made during the merger; in exchange for trackage rights on the D&H from Sunbury to Albany the C&PD was converted into a D&H/NS joint line, which cleaned up dispatching for both railroads on the Port Road.