The Quebec City-Windsor corridor is the most densely populated region in Canada. The last time I checked Wikipedia, it was reported to house about 18 million people, or about half of Canada's entire population.
So it is not surprising that there have been numerous high-speed rail studies for this corridor over the decades, as well as studies for other important links in Alberta (Edmonton-Calgary) and other parts of the country.
And yet, Canada remains the only G7 country without any high-speed rail. Though to be fair, the US doesn't have all that much either; certainly with respect to the size of its population.
However, there is some good news. In March of this year, the Government of Canada announced a Request for Expression of Interest related to high frequency rail service between Quebec City and Toronto. More information, over here.
But from what I have read, it'll be a faster upgraded service (~200 km/h), but not true high-speed rail (~250-300 km/h). I took the TGV from Marseille to Paris last summer, and this is how fast we were going:
If we're going to do this, let's be the absolute best in the world and not settle for mediocrity.