Just to get it right, county PUDs own 5 mainstem Columbia dams - Priest Rapids, Wanapum, Rock Island, Rocky Reach, and Wells. The PUDs negotiate long-term power contract sales with other utilities like Puget Sound Energy, Seattle City Light, Tacoma Power and others for the best rates they can get. If eastern WA joined Idaho, nothing would change in that regard. Those PUDs produce more power than their individual counties could ever hope to use, so they sell all that they don't use. If they raised their rates during the next contract negotiations, the buyers would just move on to the next best seller. Free market capitalism works like that, even among government owned utilities.

The federal government owns and operates Bonneville, Dalles, John Day, McNary, Chief Joseph, Grand Coulee, Ice Harbor, Lower Monumental, Little Goose, and Lower Granite. BPA markets the power for the feds, partly at market rate, and partly at lower prices to public utilities.

But I think the general idea is great. The like minded conservative rural citizens could join together and pass laws that the SCOTUS has ruled unconstitutional and have a grand old time. Until, as Todd mentioned, they run out of urban money to fund their infrastructure.