Very briefly, I would just say that wasn't a problem when I worked at Vimy Ridge. The 10 students who worked there all spoke both languages pretty well.
It was, however, a major challenge when I worked in Lower Fort Garry, because out of the 50 students who worked there in the summer, only 15 could speak French. So any time we had French-speaking visitors, they would ask for someone who was bilingual and that was the person who would take them on the tour. When I started working there, I didn't think I was at all bilingual. But I became the one responsible for those visits, because I had had the chance to improve my French skills the previous year and because I had gone to Paris the year before that. My last year there, I even gave our former Governor General a tour in French. I never would have imagined I'd be doing that when I started that job.