Bitcoin miners are only making money speculatively. No reason the power company shouldn't treat servicing them the same way.
Ughh..... come on internets. Electricity pricing policy is a very complex subject, involving everything from the ethics of cross-subsidization to the physics of power generation to the logistics of long-term capacity planning. Remember, your local power company has a government-granted monopoly on your power demand. To top it off, in this particular case the power company is a public entity (a public utility district--PUD). They definitely have an obligation to keep rates "fair", and they probably have to get approval from these guys too.
Now, reading between the lines, it sounds to me like they successfully attracted economic development to the region with their low rates, but they realized they didn't attract very good economic development. Server farms don't employee a lot of people, and these server farms might be empty warehouses overnight if Bitcoin crashes or gets regulated out of existence. The new demand will naturally raise prices, possibly forcing the PUD (or whoever operates their generation balance) to investment capital in new generation or go to market where there's not going to be any of that sweet cheap hydro for sale. So they roll a plan to target these new businesses without pissing off the incumbent customers, even though the apple storage folks presumably use a lot of power too.
I don't know enough to pick sides in this fight, though personally I'd be screaming to the PSC, FERC, and my state legislators if I moved my business to the area and then they deliberately targeted me with a price increase. The PUD may not actually expect to get their rate hike: putting up a good fight in the public eye may be their real goal, and any concessions they can squeeze out of these "outsiders" is just gravy on top. The key quote from the PUD official at the end of the article sums it up: “It would be interesting if they could provide a nexus between their businesses and economic development in the community.”