I suspect there are better fish for Metrolinx money to fry.
Of course, that's why I wouldn't have recommended building it for 15 to 20 years, even if the government had designed the new bridges differently. But if you had built the bridges to accommodate it, it would hardly cost "billions" to lay 60 km or so of track on a mostly intact, existing right of way between Barrie and Washago. Millions, hundreds of millions even, yes, but I doubt it would be multiple billions. If you're the government, I don't know how you can argue that Gravenhurst to Cochrane should get a train today, or that there's demand for 5 lanes each way in Barrie, but somehow there won't be enough demand for a Barrie to Gravenhurst GO extension 20 years from now.
GO did run to Casino Rama for a while (off the Bala sub) - nobody used it.
In point of fact, I believe that Casino Rama paid CN to run rented GO equipment as a promotional offer when Casino Rama had just opened, about a month before CN ripped up the tracks. I'm not sure if it ended because CN wanted to abandon the tracks, or because Casino Rama didn't want to keep paying for the train itself, but GO never ran service to Casino Rama. In any case, a train wouldn't just serve Casino Rama. That would be silly. It would serve north Barrie, and Orillia as well, and augment the Northlander service to Gravenhurst. The line would serve freight customers. And it would reduce traffic on the roads for those who do drive.
(EDIT: It's also not just GO. The Canadian and the Northlander could use it without stopping, which would improve their reliability by avoiding freight trains. One of the reasons I think the Northlander's service to Gravenhurst could use augmenting is that I'm sceptical, given VIA's on-time performance, about its ability to arrive on time.
I don't see the logic in GO catering to cottage-goers, either. Considering the remoteness of many cottages and vacation homes (which I would argue is the whole point), it would be less of a "last mile" and more of a "last 1/3". And at that point, you might as well just drive.
You could say the same thing about Niagara Falls, where the station is 4 km from the principal attraction. And yet, people bike, they take shuttle buses, they get picked up by friends, etc. Niagara Falls also has been given GO service, even though it already had a VIA rail stop, similar to how I envision Gravenhurst getting a GO stop in addition to the Northlander.
to serve what? The north end of a city that already has two GO stations or a city of 30-odd thousand
Orillia might only have 35,000 now, but then Uxbridge only has 22,000, and yet Metrolinx has made plans to eventually service it. Orillia might also grow a lot with a GO train, similar to how Barrie has grown. Barrie itself only has a population of 150,000 to justify its 9 round-trips.)
There is just not enough space for a curve off the current alignment onto the Highway 400 alignment
I'm not an engineer. I admit that there may be something I'm missing. But the train wouldn't have to take any curves at speed. The curve off the BCRY onto the 400 would be the tightest, and at worst you might have to expropriate part of the property south of Tiffin, east of the 400. But I can't see how you'd have to demolish an entire neighbourhood.
Anyways, as I said earlier, this is all a moot point regardless, since the bridges have already been built. It doesn't matter anymore if you could have fit a train on the 400 corridor, because the new bridges don't allow for it.