BTW, I downloaded and played your demo map, and noticed that if your controlled unit bloks the tank, it just stops and it never starts back up. It just stays in the same spot. How would you overcome that?
Have another trigger with event 'a unit idles', check its the escort unit, then order him to go to the next checkpoint. It would mean you would have to store the last point he went to so you could send him to the next one correctly.