At $16 million a mile we don't have the density.
However, we do have such density in the GTA.
Why do people go on about how such rail service would have to be "profitable". Air Canada has certainly shown that they are not profitable, with infinite numbers of bailouts, and all kinds of subsidies, coupled with monstrosities like Pearson that serve to massively clog roads in Toronto because there is no rail or public transit link with the city itself.
Then we can add in the massive damaged caused by having half filled jets spewing pollution directly into sensitve parts of the atmosphere, or the fact that Air Canada doesn't service many important and populous areas of Canada - large cities like Hamilton or London which, given the population, would have air services in pretty much every other country.
Density is such a bogus excuse - because the Russians are now looking at building a Trans-Siberian High Speed railway using Korean technology. Most progressive minded places are going high-speed, like the well known EuroStar service in Europe, the Shinkanzen in Japan, the new Korean rail service that is even faster than the TGV, or the expanding network in China. Instead, we sit back and continue to cram millions of cars and trucks onto our limited road network, and herd people onto the obsolete and unsafe airplanes that Air Canada operates - because we have this death wish to be retrograde.
No one is saying that we need to build some crazy high speed system through the Rockies - but what we really need is to have some decent service in the Windsor-Quebec City corridor, since that is the route that has the highest densities, most population, and a proven number of travellers that would entirely use a high speed train because it would be faster and more comfortable.
Sure, I can jump in the car and get to Montreal in 6 hours - blowing out much of a day in the process. It would be pretty cool if one could take the same trip on a high speed train, enjoy a nice meal on the way, and spend time using WiFi or whatever. But then again, I'd be pretty happy if they just ran a GO Train into Hamilton, rather than having to drive half the way to Toronto to catch one.
The cost per mile thing is silly, because really, how much does a highway like the 401 across the top of Toronto cost, not only in putting down pavement, but in the massive economic losses sustained because of endless gridlock and the severe damage to the environment by having a half million cars idling because some dufus wipes out their car across the highway?
Only Japan's small foot print, high population and linear geography allows it to prosper there.
Rail propers elsewhere, and in fact, the RENEF High Speed link between Madrid and Barcelona clobbers the air service there, simply because of convenience, speed and reliability. Other routes are also profitable, British Rail operates a high speed service between Scotland and London (from both Glasgow on the old western route, and Edinburgh on the old LNER route), not to mention that my cousin in London regularly takes the high speed over to Cardiff to go to football matches.
Japan doesn't have a "small footprint", Japan is longer end to end than Canada is coast to coast. Not only that, Japan has a difficult topology, coupled with the difficulty that with the exception of the standard gauge Shinkanzen, their rail network is narrow gauge, so there is no interchanging of rail vehicles. It "makes money" because the government funds it as a way of moving people around, as the topology makes highway construction expensive.
The only reason we haven't started is that our Government is controlled by special interests, like big oil and the automakers, as well as all of the payola that goes on with Air Canada.