Article L313-10 of Code of Entry and Residence of Aliens and the Right to Asylum (CESEDA) foresees that both Employee on assignment (or European Blue Card holder) and their spouses should have a resident permit card valid for the same length.
Préfectures were waiting for the Ministry of Interior to issue computer codes mandatory to deliver the 3 years card for spouses.
It seems that the codes have finally been delivered at the beginning of 2015. Since, some Préfectures have begun to deliver matching resident permit to spouses of Employee on assignment or EU Blue card holder (i.e. valid 3 years).
This is a very positive step and we are looking forward to see it implemented all over France.