We recently had an exercise, a government-industry exercise, in the United States with strong Canadian participation from the electric industry. The scenario on which that exercise was based had a simultaneous cyber and physical attack on the electric grid. I don't believe our adversaries are going to do us a favour in the future and only attack with cyber. The risk of having a combined cyber and kinetic attack—attacks on high-voltage transformers, other components of critical infrastructure that are vulnerable to physical attack—that kind of combined attack would put extraordinary stress on the infrastructure systems being attacked and could make restoration much more complicated.
On May 6th, 2014. See this statement in context.