Mont. Code Ann. § 67-10-203

If any municipality determines that the public interest and the interests of the municipality will be served by assisting any other municipality or municipalities in exercising the powers and authority granted by this chapter, such municipality may furnish assistance by gift of real or personal property or lease or loan thereof with or without charge or interest. In appropriating such property or money and providing for such assistance by taxation, the issuance of bonds, or other means, the municipality may exercise all of its powers as though used for its own direct purposes as provided in this chapter.