Well, I don't have the E473 or E425 -- at least, not yet. When I played around with an E473 in a music store, I did not see anything that would provide an automatic ramp-up/ramp-down speed effect, but I did not take a close look at it. I remember that, in some of the preview videos for the EW425, it looked and sounded like there was a Leslie speaker speeding up while the keyboardist was simply holding down notes and not manipulating any knobs, but as was mentioned back then, this could have just been some audio/video trickery on the part of whoever made the video.
Of course, keep in mind that I was looking at the E473. The video had the EW425, and that model is advertised as having more advanced organ features -- though I thought it was limited to an effect to simulate the cross-talk between adjacent B3 tone-wheels and the key click sound, but maybe there could be some enhanced Leslie simulation.