I believe GO trains can hit 90 mph between Lisgar and Milton.
And the Lakeshore West expresses. My GPS speedometer routinely hits 90mph somewhere before Clarkson.
If they're ahead of schedule or the corridor is congested, it won't happen. But if they're 2-3 minutes late, I've always seen 143kph/90mph on my iPhone GPS-speedometer app (you can download a GPS speedometer app for your phone).
In 2015, I also was on that unusually fast PanAm express train (
47-minute nonstop to Hamilton) which went 90mph most of the way and whooshed past Burlington only 30 minutes after leaving Union on a very late departure.
Given more tracks, we can have train speeds to Hamilton that
matches the offpeak Hamilton 16 Express gobus while making all stops Burlington and beyond --
on existing track speed limits today.
Seeing 90mph continuously past more than half the stations, with the stations whooshing by every 3 minutes.
It's a bit of a big infrastructure spend though, possibly resignalling the corridor to be as dense as the Georgetown Corridor, maybe more grade separations (Burloak, etc), one more extra track -- and a lot of wrangling with CN -- who owns the trackage beyond Burlington.
But it's doable to have a sub-hour train to Hamilton on existing rail speed limit. I was actually 47 minutes Union-Hamilton on a 12 coach bilevel if all the blocks are continuously clear the whole way! That is now the GOtrain of lore for me.
Alas, that particular train was poorly advertised with unclear departure signage, there were very few on the train with me -- so it will be a long time before I'm on another GO train that has a figurative Presto Log thrown into its boiler (hitting Back To The Future speeds of 88mph+).
With a faster USRC upgrade, and a faster post-Aldershot, I suspect 40-minutes Union-Hamilton is doable.
The GO train I rode was 30 minutes Union-Burlington, but 17 minutes to West Harbour. This maybe can be 26-27 minutes to Burlington with a faster Union-Exhibition section and maybe 13-14 minutes to West Harbour.
Add in Burlington and Aldershot stopping time for a "express to Burlington, allstop to Niagara", and you've got the makings of a regularly scheduled 45-minute hourly train to Hamilton if the corridor is expanded to reliably accomodate express trains.
Never seen continuously sustained 90mph since, but I still consistently see bursts to 90mph for a few minutes on many Lakeshore West "express-to-Clarkson" trains.