This happened last night for both controllers. Here is the timeline:
Power failed at around 6:30 pm.
The scheduled start time was 8:30 pm for one controller and 10:30 pm for the other.
Power was restored at 2:13 am. Both controllers logged a "Device status power cycle". Both controllers then immediately cycled through all of the zones for the previously scheduled program.
At least, this is what the Watering History tells me! I was not out and about at 2:13 am and I wouldn't have been able to tell if the sprinklers were actually running in the pouring rain. As I look at the Watering History now, I see something curious:
Do you see anything odd about that? Each of the zones completed in zero time. Also, there were no Started and Completed events recorded in the Watering History, as there are normally.
I'm now thinking that this is just an anomaly in the Watering History, rather than inappropriate watering as I thought. Sorry for the false alarm.