As you rightly pointed out, railroading in Canada was country building. It helped link the west to what we today call central Canada. There has been economic development from those days in the late 1800s, when the transcontinental was built.
The eventual arrival of a high-frequency rail will do very much the same thing. It's very different, because we're not going to move goods and people; we'll focus on people.
We can look at countries all over the world. In France, for example, the arrival of TGV has actually shrunk the country. A map exists where you can see that because of the travel times, now people can commute from cities where it was impossible in the past.
That is the kind of effect that high-frequency rail will have in Canada.