At the risk of reading too much into some dots on a vague map, maybe I gave too short a shrift to nfitz's remark about the north shore of the Ottawa. I drove that route from Oka to Ottawa through Gatineau this summer, and while much of it goes through villages and is a non-starter for HSR, you could construct a route along the abandoned ROW, up through Hawkesbury, Lachute and Mirabel, then down through Laval, avoiding the St. Lawrence mess altogether. They would need the postulated Central to Parc tunnel, but it would be for all trains, not just Quebec city. But all that's some pretty fantastic blue sky crayonning you need to do.
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