(a) The following persons shall be parties to a certification proceeding under this Article:
(1) The applicant;
(2) The Public Staff.
(b) The following persons may intervene in a certification proceeding under this Article if a petition to intervene is filed with the Commission within 100 days of the filing of the application and the petition is subsequently granted:
(1) Any State department, municipality, or county entitled to notice under G.S. 62-102(b);
(2) Any person whose land will be crossed by the proposed line;
(3) Any other person who can show a substantial interest in the certification proceeding.