if more than one automation lane is selected (lasso'ed around), and you get the automation 'boxes' with handles on the edges, you can use modifier keys (can't remember which exactly) to alter all the selected automation events [on all tracks] at once.
I have looked for this kind of function before and haven't been able to find it. If you could find out how to do this for us it would be great!
see the vid. the modifiers i used were ctrl+shift for absolute volume gain shift, and ctrl+alt+shift for the fade-in and fade-out. (i haven't figured out a way to write the same events at once with the draw [pencil] tool to both. i don't reckon that's possible at the moment and i'd consider that quite a drawback. please correct me if this is easily possible. currently if i gang all that's possible, writing common automation data still isn't covered.)