If the rig is idling, can they tow it?
Very short distance towing while idling can be done if done correctly, short distance because even if you cage all the air brake chambers so it will roll freely, you would still not be able to undo the drive shaft while it is idling, it still tries to turn even in neutral and can injure you or kill you.
But idling is not the problem. The problem is most states will not let you tow a vehicle with a live human in it. Here is where the cops were wrong for letting the tow driver even touch it with someone in it. I would never even hook up to or touch a vehicle with anyone still alive in it.
(Yes, I have towed several accidents with deceased still in them straight to the coroner’s office at the coroner’s request. Because it would have taken a couple hours and been a visual spectacle that might cause other accidents to remove all of the deceased from the vehicle and a major freeway was blocked.)
But it doesn’t matter if you are in the right or not to tow it, if you somehow jolt it around and injure that person you are in a multi-million dollar lawsuit and you will never again get an insurance company to give you coverage on any of the vehicles in your fleet. You would have to change your company name and start over like you were a new tow company. And this is NOT easy.
That tow company was stupid for even making physical contact with that truck at all with the driver still in it. If they had made him fall inside there and hit his head or break an arm they would have been screwed.