Will Ground Controls from a 3rd gen fit a 2nd gen?
yes they will, well dont quote me on that, i had ITR GC’s on koni yellows for a DA. so the GC’s were for koni’s.
that did not help you at all did it, sorry. 
i would assume yes if you also use a koni for a g3. I believe their strut is a little bit larger in diameter and you need a g3 suspension fork too.
i had DA koni’s with the ITR GC’s. GC’s are strut specific ie, all others and then koni thats how they are designed.
http://g2ic.com/forums/showthread.php?t=30796&highlight=hybrid+suspension
shows various mix and match options for a hybrid g2 suspension