Bug 44454 talked about having drag-scroll and drag-select in HTML listboxes. This is the bug asking for the same exact functionality in trees. In fact, I'd expect the fixes (or the concepts and logic behind them, at least) would be pretty similar; perhaps rod can share how he accomplished it. Please see bug 44454 for all the detail you need to know about how this functionality should work. (and by non-d&d trees, I mean trees in which you can't drag items within the tree -- if that's even possible at the moment. This is because you can't start drag-scrolling/drag-selecting AND initiate a drag at the same time)
The implementation of trees and lists are completely different. There will probably be a time in the somewhat near future where they will use the same code, but at the moment, I am afraid the the solution for list will probably not be much help to trees.
*** This bug has been marked as a duplicate of 48912 ***
Future is fine, but I don't think these are the same. This is for single- select listboxes, whereas the other is for multiselect.
*** Bug 76673 has been marked as a duplicate of this bug. ***