@Uctqnde @Hissingsid - The principle of "trickling" traffic back into a site through a period of trust building has been around for many years. My guess, and it's only a guess , is that the same thinking is behind the treatment of some returning sites with Panda.
Chances are that if the quality is greatly broadened across the sites, those high quality pages with top terms that previously ranked will start to rise again.
As usual we need more data from folks to make these stories stand up. Has anyone recovered from Panda with ALL their keywords returned ?