Mont. Code § 17-5-1517
The board may provide for the issuance of refunding obligations for refunding any obligations then outstanding that have been issued under this part, including the payment of any redemption of the obligations. The issuance of obligations, the maturities and other details, the rights of the holders, and the rights, duties, and obligations of the authority are governed by the appropriate provisions of this part that relate to the issuance of obligations. The proceeds of refunding obligations may be applied to the purchase, redemption, or payment of outstanding obligations. Pending the application of the proceeds of refunding obligations and other available funds to the payment of principal, accrued interests, and any redemption premium on the obligations being refunded and, if permitted in the resolution authorizing the issuance of the refunding obligations or in the trust agreement securing them, to the payment of interest on refunding obligations and expenses in connection with refunding, the proceeds may be invested in such securities as the board considers appropriate.
§ 17-5-1517, MCA