I don't know what the rule is in France but being here currently and riding through Paris, I can certainly say that it appears all bikers and mopeds do it and more interestingly car drivers here are expecting it.
I found it quite disconcerting initially to approach a queue and all the cars pull over to let me through, just about used to it now after a couple of trips through, but I don't ride as quickly through the traffic as the locals , so I let them get past, as I don't have the confidence in the car drivers to move out and stay out of the way.
Even when out of the city car drivers I have approached are expecting me to overtake, as they pull to the side even when there is no overtaking allowed and I am still a good safe distance behind them. It is a nice feeling to have and I'll miss it when I get back to Britain where the drivers seem more intent of making it difficult to pass them.