Not sure about W, but O class is used for red-e-deals purchased over the phone/from an agent. Also certain deeply discounted consolidator fares are in O class (ie: I once saw a extra cheap fare from STA that booked in O class). Q seems to be used by QF for connecting sectors on foreign carrier's tix (ie: if you buy an AC ticket from MEL-YVR you'd fly QF MEL-SYD to connect to AC, and they usually book in Q or L class for those). I think Q is also used for package holiday bookings, but am not 100% on that.
Hope that helps a little.
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RichardMEL, UA 1K
A Star Alliance Member.