(a) Authorization. Rates and services of a carrier must be filed in a tariff issued in that carrier's name unless they are filed:

(1) In an agent's tariff when the carrier has executed a power of attorney authorizing that individual or entity to serve as its tariff agent; or

(2) In a tariff of another carrier through issuance of a concurrence to the latter carrier authorizing the first carrier's participation in joint rates and through routes.

(b) Disclosure of authorization. If two or more carriers execute powers of attorney to the same agent, it is not necessary for those carriers to exchange concurrences to participate in joint rates in that agent's tariffs. Powers of attorney and concurrences are not to be filed with the Board, but shall be provided to any person on request.