By the way if you are in Info security infancy mode like much of SCADA security is then items like IDS take on added importance.
The main reason is that you have to have a means of learning what the threats and vulnerabilities are.
This is a particularly interesting project along those lines. I am not sure if it is still in progress but suspect it is. I was there at its inception but have not been involved for some time. Even if it is nascent Ray Parks and Sandia are leaders in the field so a visit is worth it.