Mo. Rev. Stat. § 386.230: Act as arbitrators.

Whenever any public utility has a controversy with another public utility or person and all the parties to such controversy agree in writing to submit such controversy to the commission as arbitrators, the commission shall act as such arbitrators, and after due notice to all parties interested shall proceed to hear such controversy, and their award shall be final. Parties may appear in person or by attorney before such arbitrators.