In their email they wrote:
"More accessible upgrades
Effective 21 September 2011, you can now upgrade to Diamond First Class using your Etihad Guest miles regardless of the tier level of your membership. All Coral Economy Class tickets issued on or after 1st August, 2011 will now be eligible for upgrade to Pearl Business Class.

"

I tought cool, thats a pretty nice perk. So I just called them to upgrade a eco flight I have at the end of the month and they told me, that they are unable to upgrade as it a special fare, so they are unable....

So basically they are just lying their customers straight in the face saying now you are able to upgrade all eco ticket....