I think the main factor for AF
for not even considering the A340-600 was the fact that it is not available with GE
seems to have a very strong commitment to GE
(which again might have to do with politics, as CFM is a joint company of GE
and Snecma), with all of their aircraft powered by either GE
or CFM engines. In the long run, the cost and value of the engines and related maintenance might exceed the acquisition costs of the aircraft itself.
Remember, that AF
did order the A318 (which is, IMHO, a less competitive product in its class than the A346) only after Airbus agreed on fitting some CFM56s under its wings (whereas the initial plan was to go for the PW6000 only).
It might be possible that Airlines like NWA will not consider the A346 for the same reason, i.e. not offering a PW
engines. Boeing might face some similar problems with the GE
exclusivity for the 777ER/LR.