I'll try to answer that question a little.
The Division scolaire franco-manitobaine has done some research, but I don't know if it's official. At home, the family adopts the mother's language and, if the mother is anglophone, the child will learn English. So when it comes to enrolling their five-year-old child in French school, parents realize that they could have enrolled him or her in preschool programs and activities in French, if necessary. I don't know if that answers your question.