It's been like that for boats (beyond the Free Zone) for some time now. 10 year permit, about $60 for boat and trailer. Basically, a passport for the boat. A big part of it is the Customs/Aduana thing. On the application form, you list all the major contents of the boat -- fridge, stove, radios, nav gear and other stuff of any value. Then there's never a question of having to pay duty on it. I'm sure it will be the same for RVs.
This isn't (currently) enforced in the Hassle Free zone. But, I have pulled out my TIP (Temporary Import Permit) when asked for registration while crossing at Lukeville. Guy took one look at it, compared it to the name on my passport, and I was on my way, so it does help eliminate any border inspection hassles of the boat going into Mexico. Also, you MUST have a TIP in order to check your boat into any marina south of the Hassle Free zone. San Carlos, etc.
So, while obtaining yet another piece of Mexican "official" paperwork can be a PITA, it may prove very worthwhile to you if your a frequent crosser.