In my limited experience (n = 6) I've not seen the same control system twice. I believe this is because the systems I looked at were built at quite different ti

In my limited experience (n = 6) I've not seen the same control system twice. I believe this is because the systems I looked at were built at quite different times. This probably varies a lot between countries. So your point is valid, but diversity doesn't help if the overall resilience of the grid is so low that attacking a few carefully chosen targets could cause a massive blackout.