I have been there 2 or 3 times. I was able to get the files I went to see. It has been a few years but when I went no one spoke English there and I don't speak French so it was a challenge. But, they were very helpful. First you will get a Research Card then you look up your person in index books. You will fill out a request form and go to the research room and wait.
They will call you when they find the file. You can read it and photo copy.
It was a lot of fun and really easy to navigate.