There is a Quality Score for the content network apart from the Quality Score on Google Search.
So, seems reasonable that Google Search Network might either have their own Quality Score or be included in any of the other two.
QS is influenced by performance on Google.com while performance on GSN does not effect the QS
In my experience that's true... while I've seen some GSN sites exclude some ads (don't ask me why) - I've never seen a consistently different ordering... which would indicate that GSN sites take their QS ranking (and ordering) from Google.com and other Google properties. Just my sole experience...
AWA, can you please confirm this?