I think you are wondering whether the ICC provision means what is says, in common sense language; it does. However, your problem is establishing whether your truck was under 40,000 pounds. Can an 18 wheeler come under that weight? I would suggest that you present any written proof of weight to the tow company, insist on a refund, and warn them that you will complain to the ICC about their charges in violation of the rule. If the tow company does not give you satisfaction, then present your written evidence to the ICC. Good luck.