Do these FATAR mechanisms efficiently work with Pianoteq ? I be grateful to have your opinion on this matter. Thanks in advance.

Yes, it's a very nice action but I don't think its velocity sensing is quite as good as e.g. a Yamaha and it is a pretty firm touch, something like Schubert's 3rd Impromptu in Gb Major is pretty taxing on the Fatar.  Also unless they've reworked the firmware since the initial release last year, the midi implementation is a bit rough-and-ready and sends a lot of unnecessary traffic when buttons are pressed.

Best//Neil