If HSR fares are the same as a flight then they won't be winning over very many people.
The basic problem that I see with the HSR debate is that, while it may have made economic sense 15-20 years ago when it costed $400 to fly to Ottawa from Toronto (each way), airfares have come down in the past few years so much that there is no longer very much pricing room for HSR to come in with a competitive service.
Checking Air Canada, it would cost someone $225 (after tax) to fly one way to Quebec from Toronto this coming Saturday (date chosen randomly). The flight will take 1 hour and 40 minutes. While individual flights might be more expensive (as it happens Toronto to Montreal that day is more expensive at $270), this is the sort of price range HSR must compete with. Since flying is almost always going to be faster than HSR, HSR is going to have to have a price advantage to succeed. (EDIT: Perhaps there is some price flexibility; both Porter and Air Canada want $321 (after tax) for just about any flight this week from Toronto Island to Montreal. Perhaps HSR could work at the $150-200 Toronto-Montreal price point?)
Unlike regular rail (VIA), HSR seems to be focused on providing service between major centres (Windsor, Toronto, Ottawa, Montreal, Quebec) that already have good transportation links between them and not at providing service to smaller communities (adding stops adds time). I don't see the need to spend billions of dollars to provide what we pretty much already have. (People living in Kingston might disagree with me, but I think Kingston could use better air service).
The biggest advantage airlines have over HSR for providing point-to-point travel is that they only need to build infrastructure at the points at each end of the journey. HSR must have physical infrastructure at every point along the way that must be built and maintained. As well, airports can spread their costs among many destinations -- the "Toronto-Montreal" segment of travelers is only a small percentage of the total travellers at either Pearson or Dorval.
The marginal costs of adding new destinations is low as well -- if someone decides that there should be a high speed transportation link between Ottawa and Sudbury, they just need to buy or lease some airplanes. There is already an airport at either end that they can rent space at.
EDIT: I have no objection to their being an HSR line in Ontario and Quebec, but I don't particularly want to see tax dollars going into it. If it is an economically good idea, someone will want to do it.