Tontines

I have just returned from almost 2 weeks in France and ended with a few days with English friends who have lived in France for almost 6 years. We were discussing wills and tontines and my friend told me that she didn't think that this would actually allow property to pass to a spouse rather than to family following the death of a partner. Does anyone know anything about the efficacy of tontines? Does anyone know anyone in this situation where the property has passed to the spouse or where the tontine was overruled and passed to the children. Also if this happens under French law what happens if the remaining partner wishes to move? Any advice would be welcome.