George, I think that one requirement speaks volumes. Just by requiring a sign to be listed, the NEC has added a whole series of standards to the requirements for a sign that might otherwise need to be inserted into the language of the code such as UL 48 or UL 1433.
Signs installed in our jurisdiction are required to bear a listing mark. As for sidewalk inspections, we usually don't get called for the inspection until we send the cotractor a notice of violation reminding him he has to get his sign inspected.