That's very interesting, but there's two things that they could have done (and didn't) that would have made it more convincing:
(a) use anchor text that was completely absent from the site (even the mis-spelling was used in page or url); and
(b) put up a comparison site optimised roughly the same way for the same terms and build no links to it.
Added: there's another interesting point, which is that they did make good comments that added value to popular blogs. So the ranking improvements could be user-metric based rather than link-based i.e. perhaps visitors clicked those links and Google was able to determine that - and perhaps those visitors stayed on their site a while and Google was able to determine that.