I don't care how frequent REM runs. If I want to make a trip to Quebec City from Ottawa, I don't want to transfer twice in Montreal, all my luggage in tow.
Then move all VIA service from Central to a new terminal at Cote-de-Liesse station (which would indeed require taking over some properties on the west side of the Deux-Montagnes line, and reinstating the curve through the new Stinson garage). I don't think travel times would be any worse than to Central - heck, might even be faster.
(BTW, does anyone really think of the Autoroute 40 slip roads along there being Cote-de-Liesse? In my mind they always end where the 520 ends, near Blvd Alexis-Nihon - but I've not walked around that neighbourhood much).
But that would make it difficult to serve the Drummondville service - not to mention the trains to New York.
The answer is clear really - the Trois-Rivieres HFR service will be coming around the mountain, one way or another. Would be really cool if they could go around the east side, through the Port. Would probably necessitate a new link/viaduct from near Wellington/Bourassa to the Ports ROW - though perhaps the ship has sailed on that with all the redevelopment. And reconnecting the two branches of the CP line just east of Parc Avenue - which looks pretty doable.
Yeah, probably absurdly infeasible - so Montreal to Quebec City via Lachine it is.
Would be cool though, to see VIA trains stopping at Parc station. and along by the Port. Hmm, I wonder if there's a way to get the VIA service onto the CP line at Montreal West, instead of the CN line through the yard. Topography there would be difficult where the CP and CN lines cross near Norman Street.
I do love that road tunnel though! It was a favourite decades ago, racing out to Dorval, slightly late, to catch a VIA train, in evening rush hour!