As a blanket sentence, this is complete nonsense: even if we had Hyperloops travelling between all CMAs and CAs, there would still be people insisting on driving their own cars. Instead, we should look at the modal splits and market sizes for various O-Ds and then decide where there are opportunities for the rail market share to grow…
Agree with the above; but would add, in each O-D pairing you need to examine the market you're serving (ie. tourists, vs students vs work commuters); tolerances, expectations and price points vary among these and alter the best solution.
Also, while cutting travel speeds is very important and shouldn't be under-played, that improvement requires balance with frequency, and price, and the local/regional transit offer at the destination matters as well.
For K-W, for instance, you know your largest existing market is post-secondary students/faculty, so you're looking at their particular o/d (non-Kitchener) then you know they're going to use ION to reach their Unis at the K-W end, but you have to look at its capacity/frequency to make sure it can support your service level.
For Niagara, you know tourists are your largest market, and the connection from the existing station to Clifton Hill (tourist area at the Falls) is key, as is supporting transit to other key destinations.
I would imagine for the former example that price/frequency are more important to most students than speed, though I'm sure they'd like a faster trip too if they can have it all.
While for the tourist, particularly the day tripper in the latter example, trip time is a bit more important because of how much it eats out of a finite schedule.