You can say the same about the GO train going east from Toronto and the AMT going west from Montreal.
But all kidding aside, ultimately Union Station in Toronto and Gare Centrale in Montreal would be clear hubs for high-speed rail, for subways, for commuter rail, for everything linking those two regions. The others, whether it's Ottawa, Windsor, Quebec City, Edmonton, or Calgary, are far less clear because there really isn't a transportation hub.