I've clocked Acela at just below 150mph on my GPS in between Providence and Boston. As I understand it, they would like to go faster in other sections, but the track / catenary isn't able to sustain that speed on most of the journey. Still way better than flying for BOS<->NYC or NYC<->WAS. It's a shame that the ticket prices are 2x what the regional is though.

Never heard about having dedicated rails. It would be nice, since the FRC requires any train that travels on track shared by freight to be basically built like a tank, which makes them much more expensive to make an operate.