In 1977, a competition was launched in France to come up with a new tram and reintroduce trams in many cities. A railway company (EMT) proposed this maquette (named Citadis). It was only +/- 5 years later that the decision was made for a new tram project in Nantes, but by then it was too late for EMT: the factory had already been taken over by Alstom. In 1999, Alstom launched the first Citadis low-floor tram.
Whether the name was recycled from the model in the photo: there is a suspicion but no proof.