The capacity is there if someone is smart enough to figure out how to line up the incentives. Coordination could be handled through a mining pool run by the utility, opt-in and customers have to register first. Installing the mining client from your utility could handle all of that.

The utility would know approximately how much energy a customer used for mining based on submitted shares. They would also know the address that payouts were sent to. Is that doxxing? Is it doxxing if it's a voluntary opt-in mining pool?

I'm not sure what you mean about rolling blackouts. The pool could stop handing out new jobs to some of the miners to reduce demand as needed. There wouldn't be a killswitch on the meter.