The switch to CP needs to be made just west of Chatham, ON (stop prior to Windsor), which is currently a "diamond" crossing at grade. From there it's a straight shot to the tunnel, albeit through the CP yard in Windsor.If they expect the speculated about Detroit - Toronto service to have a stop in Windsor that does not add 45 minutes to the overall running time, they will have to address the issue of building a station somewhere on the CP side between the tunnel and the junction with what now is essentially factory siding that will need to be upgraded to a main line connecting CP to CN in Windsor. Needless to say it is Canada that will have to come up with funds to do all of that, which BTW, I think they should. But of course I have what is probably less than zero say in what Canda does with its money in its territory.
https://windsorstar.com/news/local-news/cp-rail-purchases-full-control-of-detroit-river-rail-tunnelThe problem is the VIA station in Walkerville is a nice station in the wrong location. They've spent money on it, so it's not likely going away - it's just not that useful if you're going to downtown Windsor or Detroit. I can't remember for certain if the (most recent) old CP station is actually gone or has been repurposed.
CP Windsor, ON:
Amtrak at Windsor: