After the newest patch has been released I took the jump and bought the game. I started a new game and chose war plans in a way that Italy joined on the side of the central powers. On turn 2 Italy takes Nice - the Entente plays an event that some North African troops are deployed on the border to Italy et viola - now I have an Italian army AND a French corps in Nice. They co-exist peacefully and won't disappear. I think there is a bug in the event logic not checking if the provinces for the new forces are still under French control.
Any help is appreciated.