Hi Raoul,
Unfortunately, at present, we don't have all airplanes compatible with FSX. You can see the compatibility list on the Fleet page (Pilots -> Fleet, from the main site).
On 2009, that's one of our main goals: To have all fleet FSX compatible. The problem is that we have many airplanes that will need to be replaced by others, or be improved to be FSX and FS2004 compatible.... a lot of work ahead of us.
Regarding to the Croisiere Noire Event, yes, we did arranged a freeware FSX Beech 1900D specifically for the Event.
You cannot use other different model airplanes besides the ones there, but if you want, you can use your own Beech 1900D FSX to fly with it.