AEB is just controlled by a switch. So it's not an elaborate procedure to switch it ON or OFF. But I am not sure if LP's change it on the fly, or come to a halt before changing the mode.
The speed increase will mostly be for the uphill run as that has a higher speed limit than the downhill run, and also has no need to stop anywhere. For the downhill run, it would be just a lot of effort for a very small time savings, so even if feasible, they would probably not do it.