I can see a time when miners are forced to reduce power consumption during periods of peak demand. Alternatively, they may face heavy surcharges.
My vision on mining vs power plant situation: a company refuses extra clients and income (the power plant) ... no logic
Power Plants are not your average business. They can't increase their capacities in a snap. If demand suddenly goes too high - there will be a power shortage. They need to operate in a stable environment.
Power plants also have strategic meaning, so the local authorities are likely to intervene if something goes wrong.