I agree with the two previous posters: autohubs are definitely able to transfer drive torque in the forward and reverse directions.

When changing drive direction, the autohubs do disengage and re-engage, though (you will hear them clicking as this happens). I believe this to be the reason for the manual "lock" position on the autohub selector: In the rough it is possible that the direction of torque experienced by the autohub can vary (sometimes quite rapidly) as wheels loose and regain traction. This leads to high shock loads inside the autohubs as they cam out and in in response. Selecting the "lock" position prevents this by ensuring the autohubs remain engaged.

My policy is to only leave the autohubs on auto for normal tar and dirt road driving. Anything more hectic sees the wheel brace come out and "lock" selected on the autohubs.