It shall not be necessary for any person to secure authorization to hold the position of officer or director of two or more carriers if such carriers are operated under common control or management either:

(a) Pursuant to approval and authority of the ICC granted under former 49 U.S.C. 11343-44 or by the STB granted under 49 U.S.C. 11323-24; or

(b) Pursuant to an exemption authorized by the ICC under former 49 U.S.C. 10505 or by the STB under 49 U.S.C. 10502; or

(c) Pursuant to a controlling, controlled, or common control relationship which has existed between such carriers since before June 16, 1933.