As you know, priority baggage is never part of OW benefits. It is airline-dependent.
Well, yes and no, thats not quite accurate. AA always tags me with priority for LHR, but never for South America, with no regard for class flown either. And in LHR, the bags are normally almost first of, and I only do J, not F. In BOG, my bags are normally the last ones of, just about every single time. Its mind blowing.
LAN on the other hand, always tags me with a nice blue and gold priority tag and they are very good in all airports I use them with to have my bags of in a flash. Actually, they are one of OW's better airlines IMHO.