I asked Aer Lingus through Facebook and they referred me to Etiahd. I asked Etihad through Facebook and they referred me to their website. This time I managed to find this page http://www.etihad.com/en/about-us/our-partners/aer-lingus/ which seems to suggest you do earn Miles. Looks like a done deal to me... Might have to ask AmEx for a credit limit increase so I can get pay for it and get some extra Miles through them!
I'm guessing you're referring to this bit: "Members of the Etihad Guest loyalty programme are able to earn miles on Aer Lingus codeshare flights, the benefits of which are detailed more extensively on our Etihad Guest website"?
It's still not clear to me if "Aer Lingus codeshare flights" means Aer Lingus operated flights with an EY code, or Etihad operated flights with an EI code (or both).
I also find it a bit concerning that neither airline will confirm if you would earn miles of not! I think the onus should be on EY to confirm that, since you're asking about their loyalty program and therefore their rules.
Anyway, if you go for it, please report back about success or otherwise!