check out the "flip" side
Here may be a better solution. Instead of just looking into the DOT regs, take a look at the REAL issue- the court's decisions upon precident for enforcement. Remember that the law enforcement falls into the JUDICIAL system of our government. The officers can write tickets for nearly anything, but the real factor is whether they can get away with the citation in court.
If I was the one getting ticketted, I would have a lawyer not researching the DOT code, but researching the courts decisions on the DOT code. If there are none, I would take the case to the highest courts possible to establish a precident. That is the ONLY way that the law/laws will be set straight and on a uniform basis. Find out what the courts' decisions are, and that WILL be the CORRECT basis for enforcement.
If the court finds one not guilty under the law, then all are not guilty. There will be different precidents for commercial and non-commercial towing laws.
One has to use the system for their benefit, and not just bash it.
STAND UP FOR YOUR RIGHTS!!!