The convoys sit perfectly still doing nothing small distances away from warps zones. Not sure if they're waiting for someone to shoot them or the end of the universe. If you get close to them they move away from you. You can eventually move them close enough to the wh area that they can jump.

EDIT: They also go the wrong way through WH moving away from their destinations. Except that they end up doing a system jump even though they were less than 1km from the WH's center.

EDIT II: if they get caught in a storm it looks like they just get lost. Though the NPC escort makes it out fine.

Eldrad: see:

http://www.vendetta-online.com/x/msgboard/2/6682

Very different from the first post, I hadn't read the second to last one.