I'm very far from an expert on this subject, but I recall some conversations indicating that there are some fairly simple things that utilities can do to substantially harden their systems against things like cyber attacks and EMP. But apparently there are costs involved and no regulatory requirements or other incentives for taking such measures.

There's another novel out that discusses our cyber vulnerabilities with respect to our national defense. It has attracted considerable notice in navalist and strategic planning circles. It's called "Ghost Fleet" by P. W. Singer. http://www.amazon.com/Ghost-Fleet-Novel-Next-World/dp/0544142845