(2) If the territory subject to the proceeding is within the jurisdiction of two or more commissions, the highest assessed value commission shall have primary jurisdiction in the conduct of the proceeding under ORS 199.410 to 199.534, and all other commissions having jurisdiction of the territory shall cooperate in the conduct of the proceeding. On the call of the highest assessed value commission, the commissions shall meet as a joint commission to hold hearings and to adopt a final order in the proceeding. As used in this subsection, "highest assessed value commission" means the commission having jurisdiction of the greatest portion of the taxable assessed valuation of the affected territory. [1969 c.494 §10; 1971 c.462 §6; 1989 c.92 §15; 1997 c.516 §6]