Mont. Code Ann. § 50-63-103

Except as provided in 50-63-104 and 76-13-905, a person who sets or leaves a fire that spreads and damages or destroys property of any kind not belonging to the person is liable for all damages caused by the fire, and an owner of property damaged or destroyed by the fire may maintain a civil suit for the purpose of recovering damages. A person who sets or leaves a fire that threatens to spread and damage or destroy property is liable for all costs and expenses incurred, including but not limited to expenses incurred in investigation of the fire and administration of fire suppression, by the state of Montana, by any forestry association, or by any person extinguishing or preventing the spread of the fire.