Mont. Code Ann. § 85-1-221

85-1-221 . Contracts with the United States. The department may enter into contracts and leases with the United States, its instrumentalities or agencies, for the purpose of financing the construction of any works authorized by this chapter and may in those contracts or leases authorize the United States, its instrumentalities, or agencies to supervise and approve the construction, maintenance, and operation of the works or any project or portion thereof, until such times as any money expended, advanced, or loaned by said United States, its instrumentalities, or agencies and agreed to be repaid thereto by the department is fully repaid. It is a purpose and intent of this chapter that the department may accept cooperation from the United States, its instrumentalities, and agencies in the construction, maintenance, and operation and in financing the construction of any works authorized by this chapter, and the department may do all things necessary in order to avail itself of that aid, assistance, and cooperation under federal legislation now or hereafter enacted by congress.