A municipality that annexes or incorporates additional area within the service area of a motor carrier authorized by the public service commission to provide that service may not provide exclusive garbage and solid waste disposal service or impose charges or assessments for services not provided to any person or business located in the annexed or incorporated area except upon a proper showing to the public service commission that the existing carrier is unable to or refuses to provide adequate service to the annexed or incorporated area.
§ 7-2-4736, MCA