I second all that was said. But I would add one thing.
As an Anglo officer working and living in Quebec, it's not just about promotion... I firmly believe that it's the duty of an officer to be able to communicate with his soldiers in their official language.
Of course, living in Quebec, we have the advantage of being exposed to both languages from birth, but anyone should make the effort as you will encounter Franco troops all over the country.
It's not just about language, tests, and promotion, it's about leadership too!