A quick compromise that works is to use waypoints that complete when a variable is switched. For instance, a truck moves from waypoint 1 to waypoint 2. In the Condition field of waypoint 2 put something like:
movevar == 1
If at the beginning of your cam script you put movevar = 0, then whenever you want the truck to move to the next waypoint from waypoint 2, you switch the variable within the script:
movevar = 1