Maybe Etihad are trying to enhance this away already... Phoned up the Etihad Guest call centre to make an ANA redemption, operator said that he would have to take my details (membership number, flights requested, etc) as a "special team" where now dealing with these ANA bookings, and that they would call me back in 10-15 minutes max to finalise.
That was four hours ago, and I've been sitting by my phone since that first call finished (no calls received). Will give it a few more hours before calling up again, but needless to say they've left the distinct impression I've just been fobbed off.