This seems like it takes some basic facts and then jumps to a lot of conclusions without any data (like sbisker mentions) - I'm not suggesting it's BS, but it's not clear their obvious conclusions are so obvious. I'd love to see actual wage data.
You would have to somehow compare data from these companies with companies outside the group. But even then, I'm willing to bet it would show little because these companies were the big guns in the area. Very few companies would be able to outbid them in wages in the first place.
Wage data is probably not really needed here. From what I understand of the law, the mere fact that they had the agreement was illegal. Meaning they didn't even have to implement the agreement, just that they made it. That they seemed to have implemented it and attempted to hide it only adds to their problems.
A non open (or not truly open in this case) kills demand. Without demand for a finite supply (high quality engineers) the supply's worth can never fully be realized.