The OP raises a good question. I suppose it couln't be that hard for the displays to show EN/Imperial then EN/Metric then FR/Metric so that everyone is happy. That said, DJ Bitterbarn also raises the god point that most of us can simply read the French announcements to see the metric units and given that half the words are similar and thus can be guessed (Distance/Distance, Time/Temps) it shouldn't really matter.