I did a few different comparisons between a CL and a bronze account (see one example attached) for various routes (syd-hon, syd-bkk, syd-lhr) and could not see any difference in availability for the each account. I guess the difference for WP and above is the ability to put in a request to release seats.
http://i60.tinypic.com/2nv3qy8.jpg
http://i58.tinypic.com/21oyj3d.jpg