The reason given in the programme we saw about building the wings for the A380 was that once on the move, stopping for any reason would hold the whole move up for hours to get them moving again.

That sounds more like a routine thing (the wings are all of thesame size and travel the same roure), so there I would guess all the transport scenario (it may have few variants for the few wing sizes made in that factory) is preprogrammed into all the controllers on that route, they are synchronized as well, so they keep that tra sport moving smoothly. The whole sequence is tzen triggered once the load is about toleave the factory andthe dongle has then just one purpose: Keep the preprogrammed sequence in sync with the real transport movement.
So I would guess using it outside of such events would have no effect at all - just because that sequence where the dongles are supposed to work just wont be running...
The switch to green at the dongle button is just one step, the real cleanup sequence had to be started way upfront ("cleaning" the intersection,...).

The reason given in the programme we saw about building the wings for the A380 was that once on the move, stopping for any reason would hold the whole move up for hours to get them moving again.

We have a better system by the rail yards here they can actually unlock the traffic light poles and twist them around so the lights are not in the way allowing them to transport things to large to fit under the lights, and they are also able to drop them on the ground if needed but you need crane to do this, but sadly it's not automatic, but with the correct permits you can get the police to shut down the roads and intersections so there is no interruptions and for some reason people tend not to run red lights when the police are parked right there..