The LRC coaches pulled by P42 or F59 locos are rated up to 95 MPH as the banking systems have been off for several years now. The full LRC sets (locos and coaches) could easily go 100 MPH (160 km/h), the highest allowed speed on the Toronto-Montreal track (still).
Just nitpicking, but we don't tend to run F59s on the corridor. We do run F40s (up to 95mph) and P42s (up to 100mph). The LRC coaches, coupled to P42 locomotives, continue to run at 100mph as they always have, even with the banking turned off.
Couldn't we build an FRA-compliant HSR system that would follow conventional signals and rules within the cities and then switch to HSR operating mode on its own tracks once outside? Like the Acela, it would probably be a clunker compared to European and Asian high speed trains, but it would keep the capital costs reasonably low, since we would only have to build new track in rural areas.
They could be shared, but you build the overhead, the track, even the geotechnical foundation, to different standards for HSR than for commuter rail. Signalling is different. Switches are different. Ties are different.
Doesn't mean that commuter rail can't run on the higher standard infrastructure ... but it adds to the cost.
It's simply not worth putting any money into it without there being a go ahead. We could spend a fortune on it, and then discover the HSR takes a different alignment.
Other than the Shinkansen, I'm not aware of any High Speed Rail system that runs entirely on dedicated track. All high speed trains are designed to run with various types of signaling, overhead rail types, etc. It may have been a big deal to make versatile trains when the first TGVs came out, but has long since become standard.
Usually what happens is that high-speed trains use regular tracks (at regular speeds) until they reach the high speed line, where they may switch signaling or current systems.
Yes, there is a difference in the level of infrastructure for high speed railways and and commuter railways, but much of the engineering behind HSR only becomes necessary when we're talking about speeds above approximately 250km/h. Within the GTA or Greater Montreal, such speeds are highly unlikely, so the level of infrastructure can be much lower. For example, the infrastructure on the Northeast Corridor (200km/h) is rather different than the infrastructure on the Wuhan-Guangzhou High Speed Railway (350km/h). When talking about upgrading GO and AMT lines, we're talking about NEC-style improvements. That means welding the rail (already in progress), upgrading switches (also in progress) as well as smoothing and banking corners.
Commuter rail is quite capable of sharing tracks with higher speed trains. Just look at the Northeast Corridor. 135mph (217km/h) Acelas intermingle with 125mph (200km/h) Northeast Regionals and 80mph (129km/h) commuter trains. The key to doing this effectively is that the centre tracks are used by faster trains while the outer tracks are used by slower (local) trains. Local stations tend to have only side platforms (like Exhibition station) and major stations tend to have island platforms (like Oakville Station). That way they minimize the occurrence of high speed trains passing directly in front of platforms.
The Lakeshore West line is a great candidate to be upgraded to speed up intercity trains. Quad-tracking is quite feasible, and would not cost a fortune. Even if HSR doesn't get built, we will see the benefits. Although the line speed is an acceptable 95mph (153km/h), intercity trains are often forced to run slower due to freight or GO Local trains being in the way. With the line quad tracked and the signals and rails upgraded, VIA and Amtrak's P42DCs would be able to run at their full speed of 110mph(177km/h), and that's without even using electric trains. Then there's the obvious benefit that quad-tracking would vastly increase the line capacity.