I don't know that the data is publisher provided. One of the videos I watched talked about getting the data from Shelfari (not getting it on-the-fly, but sourcing it from Shelfari)
I echo the hopes for a Calibre plugin
One of the things that might make me cancel my pre-order is the thought of losing all the Calibe/plugin goodness that I currently use on my K3
ETA - yes, Shelfari does seem to be the source. In this video, at about the 2:05 mark he starts demoing x-ray, and a few seconds later he mentions Shelfari.