Unfortunately the star file rules call out the airlines and fare codes to use for booking for an involuntary downgrade, and you get Y only on AE, IB, LA, and I forget which other one (maybe AY); not on BA -- despite many UK flights being 1 class -- or on QF. Until they change this you are stuck with needing L inventory when A or D is not available. One of the drawbacks of the OWE tickets. My own experience is that if inventory is not available when you initially try to book, it only gets worse closer to travel time. So if you are required to travel on a specific date (in my case often a specific flight) there is poor odds in going standby. A sharp contrast to the involuntary reroute situation, where these fares really shine and you get to be at the top of the list (presuming A fare and Emerald status).