I doubt if stand alone illegals could afford truck and insurance for the most part. Could some asshole small operation hire the occasional illegal, as working cheap and maybe even assist with getting CDL? (Afterall, you gotta have a Commercial vehicle to be tested for a commercial license) Sure. Don't forget the renegade truck school, that might be assisting also. But, come what may, you won't get past a weigh state inspection, random roadside, or a state trooper stop without insurance as you will be locked down, on the spot. So, insurance companies do insure fleets and fleet drivers, small and large, and give guidance to companies, even if the insurance company does nothing more that process claims for the company, with the company actually self insured, paying any claims and represented in court (if necessary) by company retained lawyers, not insurance company lawyers.