buster52,
If you are serious about wanting to know how this tax exception works, Google "ca publication 52". Everything you need to know about this program is described in this document in vivid detail. It is perfectly legal, but not easy to actualize if you are currently employed since you must show proof of use outside the state of California for at least a year. You cannot simply store it outside CA and qualify. We kept our rig outside CA for four years and used it as much as we could to make sure we met the qualifications.