You might get harassed, or an uneducated cop might even ticket you, but you would get off on a technicality. There was a federal supreme court decision back in the 70s that determined that an RV is in its own class and is not classified as a truck. This means that any regulation must specifically call out a motorhome somewhere in the law. (often times the definitions of terms are given as a preface for the law)
My advice would be to use common sense. Generally speaking, use the truck lane. Now of course if you want to pass a truck on the right, you have the legal right to do so, but it may not be the wisest choice, especially if you are about to go under an overpass, you don't want to be next to a semi when the lane goes narrow.
