Without seeing the merger and assumption agreement and without knowing the D&Hs final independent formal structure I'm not sure anybody could truly answer your question.
For example much of the trackage that the D&H originally had was leased. Had all those lease been bought out or terminated before the D&H merged with CP. The D&H itself may have had subsidiaries on the books for accounting reason.
And then there are the trackage agreements from the Conrail creation, what leases, agreements etc did the D&H acquire or agree to with that.
Then of course you had the damage done by Guilford. What did they modify or strip out?
It gets to be a very tangled web when it comes to corporate accounting that stretches back over decades.
For example a corporation I worked for merged with another corporation, yet we still had on the books, for depreciation purposes, a small subsidiary company that held a massive amount of property. It was a legal corporation, with 1 employee, who's board just happened to be the BOD for the parent corporation. But it was a separate company.
For all intents and purposes, even if it is legally a separate corporation, the D&H is a sub of CP controlled by the CP management with no independent decision making ability. Even if it owns separate properties (say like Kenwood Yard) or equipment for accounting purposes. It may even be a separate corporation for the purposes of paying its American employees.
But CP treats it, operationally, just like another division. Who knows there may be a CP holding company that 'actually' owns all its American properties with all its stock held by the parent corp. Seen it done many times for tax purposes.