Both yes and no.
Yes because CP bought the CMQ back when very few people expected them to do so. Yes because CP certainly wouldn't have had to spend upwards of $200 million to purchase and rebuild the CMQ. Yes because CP would have been able to better compete against CN by getting in on the Port of Saint John expansion earlier. Hunter Harrison, love him or hate him, saw the sale of the lines east of Montreal as a massive strategic mistake and he was right.
No, because at the time they were sold, the lines east of Montreal were always an operational headache serving a barren territory with little to no traffic. This was only exacerbated by the de-industrialization of Maine and the Maritimes in the latter half of the 20th century. They simply weren't profitable anymore. CP tried to make them profitable by setting up the Canadian Atlantic Railway, a subsidiary complete with its own marketing department; however, it failed. It was a lost cause, at least at the time. Plus, CP thought it could take all that traffic bound for the Port of Saint John and reroute it to New York/New Jersey via the D&H, making it profitable. CP's thought process was why waste millions of dollars per year on an unprofitable line to a small port when we have access to the largest port on the Eastern Seaboard?
Now of course CP's plans for the D&H never panned out. Despite its best efforts and what seemed like infinite patience, it remained unprofitable right up until most of it was sold in 2015. To paraphrase Norfolk Southern's famous VP for Strategic Planning Jim McClellan. "CP bought the D&H, god knows why they bothered. They spun-off a low-density network in Maine and the Maritimes only to turn around and buy a low-density network in the Northeast."
The Irving Roads (Maine Northern, Eastern Maine, New Brunswick Southern) will never be sold back to CP or any other railroad for that matter. First of all, the Irving Family's business mentality is that if you buy something, you keep it. Second, before CP-CMQ and CSX-PAR, the Irving Roads were a local operation mostly focusing on forestry products. With the introduction of two Class I railroads that both want access to the expanding Port of Saint John, the Irving Roads are set to become quite the "cash cow" in the next few years. They will become a Maine/Maritime version of the Florida East Coast. A highly-profitable, highly-strategic, independent property that survives by playing to a niche.
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