Happy Canada Day (or as we prefer to say here in Quebec:
National Moving Day)!
Just a few comments from me, trying to recall the spirit in which HFR was created as an idea while suppressing any attempt to speculate where the joint project office might be heading. IIRC, the key idea of HFR was to create a project which was large enough to make a real change (i.e. to enable significant growth in ridership and revenues) while small enough to have a realistic chance of receiving the funding it needs. It therefore deliberately accepted the trade-offs which deviate from what some people here feel “would be right” (such as double-tracking, grade separation of all level crossings or electrication) and left them as “upgrades” which could be added at a later point. Similarly, in terms of providing a path towards HSR, the emphasis was to minimize waste (i.e. infrastructure work which can’t be upgraded to HSR) rather than future-proofing every single infrastructure work. Nevertheless, such add-ons or HSR-enablers could have been added at any time, including the initial construction phase, providing that investors (public or private) were willing to pay for it.
Therefore, the Stouffville line could show a cheaper alignment from Agincourt Yard into Union Station, requiring only little engineering works over what would be required for Metrolinx anyways, while accessing a better transit hub (Kennedy vs. Eglinton). Sure, with Metrolinx’ long-term plans, this corridor might get too crowded, but until then, this routing could reduce the price tag for HFR, while only having minimal negative effect on travel time (considering that the shared section between the intersection with CP’s Belleville Sub and Scarborough Junction would only be 7 km long and so far has no other stations than Kennedy). And once traffic on the Stouffville Sub grows beyond what would make VIA’s presence tolerable, the only engineering work no longer be operationally required would be the ramp between Belleville and Stouffville Sub, but could still provide operational flexibility in the case that there is any disruption in the Don Valley.
Conversely, bypassing Ottawa with Montreal-Toronto express trains undermines the key trick to minimize operating costs and fleet size: by merging the Montreal-Ottawa, Montreal-Toronto and Ottawa-Toronto trains into one one single corridor, while outsourcing the intermediary markets onto separate, less frequent but all-stop Regional services. Bypassing Ottawa therefore does not only escalate construction costs (by increasing the length of the HFR infrastructure), but also operating costs (by driving up train-miles and fleet size).
Finally, the Alexandria Sub is already built to close-to-HFR standards and has historically allowed travel times (1:35h) close to those envisioned by HFR. Therefore, rebuilding a parallel corridor to save just a couple of minutes would be contrary to any of the principles I’ve outlined above. Not to mention building a greenfield connection from the Havelock Sub to Oshawa...
Just in case I wasn’t clear enough, I’m solely drawing from the conceptual principles under which HFR was conceived, not whatever principles the Joint Project Team may be working under, but I believe that whatever project will emerge from the ongoing studies and design process will still have a noticeable resemblance with that initial idea I’ve outlined above...