This too is a very good question. What is perfectly clear is that many of these immigrants have a knowledge of English that is probably inadequate when they arrive. Many of them have mentioned that they consider it very important to integrate into the French-language community, but that to enter the labour market, they also have to develop language skills in English.
It's a paradox then, because to maintain the vitality of the French-language community, proficiency in both languages is required to better integrate into that community.