There would only be one station, though with two distinct areas - one for VIA and one for Amtrak.
I'm really, really, suprised (and impressed) that it could get from the existing Amtrak station, to the existing VIA station, in only 15 minutes.
The main Amtrak Detroit station at Woodward and East Baltimore?
So after it arrives there from Dearborn (Dearborn Transit Center) it would have to back out the Grand Trunk (CN) track from the station - for 4 km, and then change, presumably through low-speed switches, to the North Yard Branch, and do 1.5 km and two very tight curves onto the old Michigan Central line, through the tunnel (about 3 km to the border), onto the CP track for 4 km and then change to the Essex Terminal Railway for 5.5 km to the VIA track. And then change direction again for 2 km into the VIA Windsor station? Almost 20 km! In 15-minutes!
That makes VIA's 20-minute 18-km tour-de-Montreal from Dorval Station to Central Station look like a cakewalk!
They could save some time by not using the Amtrak station in Detroit, and then built new platforms where the Michigan Central Detroit Station platforms were - but you still have to do 13-km, through the tunnel, and over some slow track, before reversing direction to the VIA station.
Wouldn't it be simpler to just rebuild the Michigan Central Windsor station, and put the border stuff there. And after clearing customs for the train to wind slowly to the VIA station (though surely a bus bridge, or a 5-minute taxi ride woud make more economic sense.
They don't care. I once had a reason to take the bus to Syracuse from Toronto. It crossed at Queenston Lewiston into the US.
Someone had entry denied by US border agents and they told her to leave and walk back across the bridge to Canada.
She said "But how can I get home?"
The response was simply "I don't care. Leave right now without saying anything more or we arrest you for immigration fraud and put you in jail while awaiting court hearings."
This happened something like eight years ago. I imagine it's worse now.
Are you sure this was the Lewiston Bridge? Did it used to have a sidewalk?
I'd have thought that bus traffic would have used the Rainbow Bridge.