Disclaimer: it's not my site I'm discussing and I don't have access to server logs(or Google's crystal ball) but I can say that I've just witnessed a site make an apparent huge recovery and then some. I've also seen the changes made to get the new higher rankings which is what I'll mention here. There doesn't seem to be any new spike in backlinks.
The site, according to its owner, was hit rather harshly by Panda earlier this year(verious SEO tools agree) despite having original articles and not doing anything blackhat to speak of. After losing 50% of his traffic the owner added 75(!) links at the bottom of every page to other important pages. These 75 links are in addition to the 35 he added to the sitebar which already had 35. In total each page has 110 new internal links, 145 per page in total, and nothing else has changed.
The site now has more traffic than it did before being pandalized and, more importantly, is now top 3 for a good number of impressive keywords. Surely the increase in internal links can't be the reason?