I've actually had really good luck lately with CX (as an AA EXP). in the last 2 months I'm 2/4 for Op ups from W to J on LAX-HKG routes and even got a Y to J bump on a KA 330 (very unexpected).

I think the sweet spot is LAX routes and booking PEY. I generally fly Sundays out and Saturday returns so probably a bit lighter on elite travelers too. If I don't get a bump up they do try and block a seat next to me as well. That said, my initial luck has spoiled me a bit. I don't expect it, but always check my reservation 10 minutes before boarding now to see if I got moved, almost wish I could forget I ever got one so it would be a fun surprise every time (it's still pretty fun).

Never had any luck on JAL, and don't fly too many other affiliates. That said I think it will be interesting as I know of a few AA EXPs (myself included) who are booking affiliate carriers in PEY instead of AA economy tickets. I figure with fewer SWU's and at least a decent seat coupled with the better EQD and RDM equation a lot of Oneworld partners will likely see an uptick in PEY loads from the US...