It is only one data point, but I was pleasantly surprised how easy it was to book open jaw saver award roundtrips for me and Mrs FC ORD. Flying in December, ORD - ARN on SAS and returning MUC - ORD on UA. 1K Desk / International Reservations checked several dates for me and all had award availability.
Did only needing one leg on a *A carrier help my cause, is less blocking occurring, or did I just get lucky? (or who wants to go to Stockholm in mid December)