Mont. Code Ann. § 25-10-303

In an action involving solely the recovery of property damages arising out of the ownership, maintenance, or use of a motor vehicle, in which the plaintiff secures a judgment equal to or greater than the amount of damages claimed by the plaintiff in the plaintiff's last written offer to the defendant or the defendant's agent prior to the filing of the cause of action, the court shall allow plaintiff's reasonable attorney fees, which must be fixed by the court, notwithstanding any agreement between the parties to the contrary. If the defendant or the defendant's agent fails to make any offer within 15 days of the date requested to do so by the plaintiff, the plaintiff may file the cause of action and, if successful in the action, is entitled to reasonable attorney fees under this section.