Mont. Code Ann. § 15-6-215

Except as provided in 15-24-305 and 61-3-520, all property, including vehicles, brought into the state or otherwise used for the exclusive purpose of filming motion pictures or television commercials is exempt from property taxation and registration fees under 61-3-321 (2), provided that the property does not remain in the state for a period in excess of 180 consecutive days in a calendar year.