California Code, Public Utilities Code - PUC § 733

(a) If the common carriers do not agree upon the division between them of the joint rates, fares, or charges established by the commission over through routes, the commission shall, after hearing, by supplemental order, establish that division.  Where any railroad, or passenger stage corporation that is made a party to a through route has itself over its own line an equally satisfactory through route between the termini of the through route established, that railroad, or passenger stage corporation may require as its division of the joint rate, fare, or charge its local rate, fare, or charge over the portion of its line comprised in the through route, and the commission may, in its discretion, allow to that railroad or passenger stage corporation, more than its local rate, fare, or charge if the commission determines that it will be equitable so to do.  The commission may establish and fix through routes and joint rates, fares, or charges over common carriers and stage or auto stage lines which may not be otherwise subject to the provisions of this part, and may fix the division of those joint rates, fares, or charges.

(b) Subdivision (a) is not applicable to network railroad transportation.