Like many basic tenets in railroading economics and traffic, I don't think much has changed into this present time. Railroads make good money when they originate a "railroad commodity" (heavy &/or, voluminous &/or, long-haul, etc.), like Maine printing paper. From the way things have progressed, I'd have to say that Pan Am, too, views the world through the eyes of its "MEC" franchise, that is, that's where their money is, while the ex-B&M freight main west of Ayer is a lower-profit bridge route from Maine to the NS and the short-haul terminating road for NS. The D&H remains in a tough spot as a bridge road for NS and CP, the least profitable, in general, traffic to haul.
IMHO, PAS will "succeed" by bringing Pan Am's west end (and their access to N.E.) from the brink of collapse and riding the rising tides of increasing freight rail demand (in a long-haul market) and CSX's strategic rate increases aimed at improved financial performance, though not for the higher-rated, premium traffic held by CSX's big competitive advantage.