Things
have changed
When I was an ATCA11 at Manchester [Many moons ago] I was a "Runway Controller", and I was qualified to clear vehicles to cross the Runway. The only thing that I had to ask the ATCO was to clear a tug towing an a/c..because I didn't have clear sight of said tug... because I was in a Runway Caravan, alongside the Runway...
Just a BOFs viewpoint