Yes, I'm wondering, too. So far I can't find anything on the IRS, SEC, CFTC, NFA or Eurex web sites that specifically addresses this, and my broker understandably isn't interested to take a position either.
My failure to find anything doesn't mean such information is not there, but I am puzzled. In the absence of any clear guidance, I would think the prudent approach would be to treat them as other Section 1256 futures contracts.
But if someone has specific understanding to the contrary, I'm all ears.