You're kind of handwaving away the fact that most of the country lives in major centres.
Connecting just the majoriest of cities, the Vancouver, Calgary, Edmonton, Regina, Saskatoon, Winnipeg, Toronto/Hamilton, Ottawa, Montreal, Quebec, and Halifax metro areas would cover, by some quick math, over half the country's population already. You'd get a good chunk more if you add in the rest of the Golden Horseshoe - Waterloo/Kitchener, London, Windsor, Kingston - and a few other major regional centres (your Sudburys or what have you) to break up the trip.
A hub-and-spoke model - with high-speed rail connecting those major centres, conventional rail connecting those to smaller - but still regionally significant - large cities like Kelowna and Kamloops, and then buses from there to further flung places would easily cover a more-than-sizable majority of the country's travel needs.
On the one hand - part of the reason for poor ridership - and thus poor cost efficiency - of buses and trains is a consequence of a 20th century planning mindset that prioritized car infrastructure. And it was a vicious cycle. Service was infrequent and slow, so people preferred cars; people preferred cars, so more infrastructure was built for cars; fewer people road the trains or buses, so economies of scale got worse, service was made even more infrequent and funded even less...so more people buy cars. More people will ride trains and take buses if they run more frequent and are faster, especially as the cost of operating a personal vehicle has gone up. If you build it they'll come and all.
But on the other hand, to me much of your cost analysis is moot. Trains and buses won't make much money in ticket sales - well, so what? How much do roads for cars make in "ticket sales"? The governments have happily funded car-related infrastructure for decades despite the fact that they don't, directly, get a penny back from it. Why do rail and bus have to play by different rules?