ORS § 225.470
In addition to the powers otherwise conferred on cities of this state, a city that owns or operates an electric light and power system, or a city that owns or operates an electric cogeneration facility as defined in ORS 758.505, may plan, finance, construct, acquire, operate, own and maintain an undivided interest in common facilities within or without the state jointly with one or more other cities, with one or more districts, with one or more electric cooperatives or with one or more persons, or with any combination of such cities, districts, electric cooperatives or persons, and may make such plans and enter into such contracts and agreements as are necessary or appropriate for such joint planning, financing, construction, acquisition, operation, ownership or maintenance.
ORS 225.470