Wash. Rev. Code § 80.36.160

In order to provide toll telephone service where no such service is available, or to promote the most expeditious handling or most direct routing of toll messages and conversations, or to prevent arbitrary or unreasonable practices which may result in the failure to utilize the toll facilities of all telecommunications companies equitably and effectively, the commission may, on its own motion, or upon complaint, notwithstanding any contract or arrangement between telecommunications companies, investigate, ascertain and, after hearing, by order (1) require the construction and maintenance of suitable connections between telephone lines for the transfer of messages and conversations at a common point or points and, if the companies affected fail to agree on the proportion of the cost thereof to be borne by each such company, prescribe said proportion of cost to be borne by each; and/or (2) prescribe the routing of toll messages and conversations over such connections and the practices and regulations to be followed with respect to such routing; and/or (3) establish reasonable joint rates or charges by or over said lines and connections and just, reasonable and equitable divisions thereof as between the telecommunications companies participating therein.

This section shall not be construed as conferring on the commission jurisdiction, supervision or control of the rates, service or facilities of any mutual, cooperative or farmer line company or association, except for the purpose of carrying out the provisions of this section.