For certain fare buckets you can have some luck (if you know what you are looking for) using the ITA tools at http://matrix.itasoftware.com/cvg/dispatch/

There are some details about how to use it correctly at: http://www.flyertalk.com/forum/showthread.php?t=278091

Additionally it has an undocumented feature that allows you to specify specific fare buckets. If you want to, for instance, search for A bucket availability on the HKG-JFK route on Cathay Pacific you would enter the search as From: HKG:: cx+ / f bc=a and To: JFK:: cx+ / f bc=a. You can substitute the "cx" with the proper airline code for the airline you wish to check, and substitute the "bc=a" with "bc=X" where X is the fare bucket you wish to check. If you wish to check multiple booking-codes and not place any restriction on the airline format the request as JFK::/ f bc=x|bc=y|bc=z to check the x, y, and z buckets.

I forget which fare bucket Cathay uses for its reward seats, but I am sure someone else on this board can tell you that, and will.

Cheers!