I have an open-jaw booking (LHR-VIE in Dec, GIB-LHR in Sept) with the LHR flight on New Year's Eve. I reduced the cost by £20 by using 3,000 Avios, so I imagine this means my flight is not eligible...no bonus in my account anyway.
I guess I'll have to drown my sorrows with a T3 lounge crawl on New Year's Eve!