if you have english on the cue ball it will pick up speed off the rail
That's true for any rail. I was just assuming zero spin.
I think that normal rails are so inefficient, that everyone perceives the CB to pick-up speed, when it just "loses less."
To be completely honest so I don't sound like a know-it-all, I thought the CB picked up speed too until Greg Sullivan gave me a physics lesson when I asked him the same question.