When a person affixes the person's property to the land of another without an agreement permitting the person to remove it, the thing affixed, except as provided in 70-18-102 and in the Uniform Commercial Code, belongs to the owner of the land unless the owner of the land chooses to require the person to remove it.
Fixture Attached By Other -- Accession By Owner
Mont. Code Ann. § 70-18-101, under Fixtures.
Mont. Code Ann. § 70-18-101