I only see any chance of this happening if Ford really goes ahead with refurbishing Detroit's Michigan Central Station with all the border facilities needed to clear US and Canadian customs.
There's been nothing specific on restoring the train depot components to active use, that I'm aware of; but to be clear, the project of restoring the building is well under way and has been for some time.
Ford has also expressly suggested retaining some future ability for train service, though by no means as a major station (they contemplated removing several tracks/platforms as I recall, but don't hold me to that)
And even then, I only see existing VIA trains extended to Detroit, where passengers would clear customs before boarding / after detraining a VIA train in Detroit.
To be clear, I defer to your knowledge in this area, but ask sincerely:
Why would it be organized that way?
The Maple Leaf doesn't unload all its passengers to be picked up by a separate train (though the customs situations is terrible and there is a crew change).
Amtrak runs (relatively) seemless service on the west coast to Vancouver and to Montreal.
There's clearly a customs issue to work out; but I would imagine using a single train set and switching crews if required).
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By no means am I opposed to have VIA start a run in Detroit, if the business case is there and travel times can be reliable; but that's not what I was imagining in terms of an Amtrak service to Toronto.
In order to allow for sufficient time to clear customs (and account for delayed inbound trains) a transfer time of 90-120 minutes seems desirable. If we look at the pre-Covid schedules (and assume that VIA trains still serve the station in Walkerville, with a 15 minute dwell time and a 45 minute travel time onwards to Detroit), this would result in a transfer time of 3 hours Eastbound, but 6 hours Westbound:
View attachment 376412
Not that easy to schedule convenient connections in Detroit with only three trains operating to Chicago, but I believe I read that Amtrak wants to increase that to six round-trips, which should provide for much more flexibility...
As noted, I'm imagining this differently.
I also imagine, if VIA were to service Detroit, it would make far more sense to return the station to its original site and then transfer to owned trackage along existing or new connections as appropriate.
Serving Walkerville would seem cumbersome, but perhaps that's just me.