CSX has done almost everything under the sun to prevent Amtrak picking up higher speeds along the WLR corridor west of Albany.
"Upgrade the track? Nah, it's good for our 60mph max intermodals. Live with it."
Build out a third track for Amtrak's exclusive use? I think CSX half-heartedly "agreed" to that knowing full well it wouldn't happen. They required a minimum clearance to CSX's tracks. I don't remember the details of this one, but I think it fell slightly outside of where the 4th track used to sit, and would've caused problems anywhere there was a third track/passing siding. Not to mention the places where it would have interfered with the yards.
Here's the thing to remember with that, every time someone brings up the "but it used to be 4 tracks!" argument -- On this portion of the WLR, New York Central ran all passenger trains on the southern tracks (2 and 1) and all freights on the northern tracks (3 and 4, running "left handed"). While there were safety reasons in this little experiment (preventing high-speed sideswipes if a freight load leaned into the passenger tracks), it also meant that they could build all of their freight yards to the north and all their passenger stations to the south, so there was never interference between the passenger and freight trains when making stops. When they installed the CTC to begin running two-direction tracks, they ripped out 3 and 4 as they were obviously the slower speed tracks and in worse condition. But all the yards and stations remained where they were, and for the most part are still where they are today. The only location within the ROW that Amtrak/NYS could even hope to build out an HSR track would be on the north side, which would mean having to figure out how to bypass all the yards on the north and rebuild all their stations to the north as well, or interfere with CSX at every station and yard along the route, which no doubt would slash the time benefits of hitting 100mph along the way.
There's portions of old ROWs that they could piecemeal together to create something resembling a separate route that still hits most of the cities --
- Lehigh from Buffalo to Batavia
- Lehigh or Peanut or Erie from Batavia to Leroy/P&L
- Strike a deal with G&W to use the old B&O line into Rochester
- A lot of the old West Shore from east of Rochester to Albany
- Some other random pieces here and there, such as the SusieQ into Utica...
-- But you'd still end up running on CSX trackage into and out of the cities to hit existing stations, or rebuilding new stations outside of the area. And while some sections like the Lehigh between Buffalo and Batavia are straight as an arrow, the West Shore is anything but, so I doubt you'd ever hit 100mph most of that way. Best you could hope for is less chance of losing slots with CSX so you don't end up sitting on a siding waiting for 4 freights to lumber by before you can make it into the next station.
Edit: And let's not forget about NIMBYs along those abandoned ROWs I mentioned...
Much as I'd like to see it, realistically HSR ALB-BUF is an idea as dead as ever seeing passenger traffic in BCT again.