Right I can confirm that my G27 pedals that are inverted, work with the Fanatec CSR. However I have been experiencing some issues like when releasing either the gas/brake, it still flickers.
I tried it on GT5, and the same thing happens, when on full throttle, the car kind of holds the brake pedal on and it cause acceleration problems.
Can anyone else just confirm that the Logitech pedals work fine on both Forza 4 and GT5, because I may have to phone up Fanatec soon and complain.