Utilities that have acquired an electric energy conversion facility site or electric transmission line route in accordance with the provisions of this chapter may proceed to construct or improve such site or route for the intended purposes at any time, subject to subsections 2 and 3 of section 49-22-16; provided, that if such construction and improvement commences more than four years after a certificate or permit for the site or route has been issued, then the utility must certify to the commission that such site or route continues to meet the conditions upon which the certificate of site compatibility or electric transmission facility construction permit was issued.