Curfew seems excessive. We have had a number of 8-12 hour power outages around here and the local governments have never declared curfew. Parts of Ottawa were without power in the spring for 2 weeks after the derecho and there was no curfew.
Consider that the curfew could be caused not by the outages, but by the fact that there could be further attacks, or the suspicion that whoever did this wanted the outage as a first step for a more extensive plan.
It's far more likely to be vandalism, and that happens from time to time with infrastructure all over the place. Jumping to such an extreme overreaction does nothing other than make life miserable for everyone that's innocent. Deploy police to monitor infrastructure for sure, but locking down law abiding citizens seems like overkill.
