I saw this 'guerrilla campaign' the other day at brandinfection.com. But I totally forgot about it until reading Jeff Staples blog today.
It's my understanding that it was done by the FTW crew (Mr. Talon, Baveux Prod. ,Kone and Epoxy) in a Berlin rail station. I'll be the first to admit I know nothing about them.
But the classic wheatpasting to convert the subway billboard into a over sized monitor is truly brilliant. The alteration of Britney Spears, Leona Lewis and Christina Aguilera is, as coolhunting put, "a gentle reminder of our urban airbrushed landscape". The concept was flawlessly executed and I would imagine a nice change of scenery.