With respect to any matter of fact or law at issue in a contested case and notwithstanding any other provision of law, a member, staff, or agent of the Public Service Commission shall not during the pendency of any contested case heard before the commission have any ex parte communication with any party having an interest in the outcome of the contested case. For purposes of this section, the definitions in section 84-901 shall apply. Notwithstanding subdivision (4)(c) of section 84-901, this section applies to all communications by a party in contested cases under the State Natural Gas Regulation Act, including, but not limited to, general rate filings under section 66-1838.