Announced today, though it feels like it’s been talked about for decades already, and I can imagine any incoming government of a different political persuasion cancelling it immediately…
So, as was mentioned counting is still ongoing. However, unless a coalition between the Conservatives and the Liberals is formed, it looks most likely to be a Liberal Government, either with an outright majority, or relying on the support of the NPD (or Bloc Québécois, though that seems unlikely).
In either case, it appears highly likely that these initial plans will go ahead (yay). That's step one. However, given it's a six-year plan, unless they manage to get shovels in the ground somewhere in the next few years ahead of the design and development plan concluding or enter into contractual agreements with private investors that are difficult to walk back on, I don't see how it will survive the next government to be elected somewhere between now and 2029.

Projects like these really are a nerve-wrecking affair. Almost seems like you never know if it's actually going to happen until opening day comes.
Hard to predict how Canadian politics may evolve, but I think it's likely the Conservatives will win the next election, albeit perhaps not an outright majority, if the Trump phenomenon still lingers. I would so want to live in a world where public transport was largely apolitical and there was cross-party support for projects like this, I really do, but alas, we don't (yet).
Still, let's hope someday Canadians, everyone from students, families with kids, business leaders, politicians and pensioners, will all be wizzing from Montreal to Toronto at 200mph, comfortably and quietly, with free wifi, all the mod-cons and a train leaving every 20-30 min or so. The talks of cancelling the project, at that point, merely a distant memory...