Neb. Rev. Stat. § 18-2434

In any suit, action, or proceeding involving the validity or enforcement of, or relating to, any contract of the agency, the agency shall be conclusively deemed to have been established, except as against the state, in accordance with sections 18-2401 to 18-2485 upon proof of the issuance of the certificate issued by the Nebraska Power Review Board. A copy of such certificate duly certified by the Nebraska Power Review Board shall be admissible in evidence in any such suit, action, or proceeding and shall be conclusive proof of the filing and contents thereof.