The Nebraska Real Estate License Act shall not apply to railroads and other public utilities regulated by the State of Nebraska, or their subsidiaries or affiliated corporations, or to the officers or regular employees thereof, unless performance of any of the acts described in subdivision (2) of section 81-885.01 is in connection with the sale, purchase, lease, or other disposition of real estate or investment therein unrelated to the principal business activity of such railroad or other public utility or affiliated or subsidiary corporation thereof.