Not trying to sink anyone's battleship. I've seen others move a bit faster up there on occasion, so my first guess is that track conditions are better than what they were and that no one is working up there at night as opposed to during the day these last few months. Maybe P&W moves faster because their engines are better pullers for all I know. though
now that I think more about it, it's probably very simple: they come in with loads, downhill in queens, and out with empties, less weight for the engines to drag uphill on the way out. Csx and CP don't have that luxary. the loads out slow them down (or in csx's case, cause the occasional stall)
And if not they're not moving within regulation, well, not to sound like too much of a nimby, but I don't think anyone would want to see anything derail up there. Yes, amtrak moves way faster up there, but their track is concrete ties and probably able to handle faster speeds than they use.
CP hit the ground not too far down the line what, a month ago?
Keep in mind 10-15mph faster than cp or csx is still at or around 25mph total, since the others only seem to do 5 to 10... the track is probably good for that much, or so I'd hope. I don't know how good that track is, which is why I ask.