Mont. Code Ann. § 10-3-1113

In any case or controversy involving performance or interpretation of or liability under a mutual aid agreement entered into between one or more fire protection services, emergency medical care providers, or local government subdivisions of this state and one or more fire protection services, emergency medical care providers, or local government subdivisions of another state or of the United States, the parties to the agreement are the real parties in interest. This state may maintain an action against any fire protection service, emergency medical care provider, or local government subdivision whose default, failure, performance, or other conduct caused or contributed to a liability incurred by the state.