My understanding is that in order to comply with the new legislation at the start of the year, many commercial places culled all their birds, gutted the complex and refurbished to meet new requirements, rather than having a regular turnover barn by barn. It would be cheaper that way with one contractor coming in for a large job too.
So restocking for 1 January 2012, most birds will not be spent until the end of the year at least, possiby next summer depending on the policy on turnover/replacement age.. I would imagine there are thus fewer birds available for rehoming tho there will still be some from facilities that were less intensive or managed through inhouse staff to secure the changes in cage size etc in advance of January.