(a) Nothing in Sections 556 to 558, inclusive, shall limit or modify the duty of a common carrier to establish joint rates, fares, and charges for the transportation of passengers and property over the lines owned, operated, controlled, or leased by it and the lines of other common carriers, or the power of the commission to require the establishment of such joint rates, fares, and charges.
(b) Subdivision (a) is not applicable to network railroad transportation.