Filmed largely in Rome rather than Nice?

This has been one of my favourite films for a long time and when I was recently in Nice I tried to track down some of the filming locations, but largely came up empty handed, it was like a lot of the locations set in Nice didn't exist in the city.

So I downloaded an HD version of the film from itunes to see if I could read any of the road names. There were a couple of these, including 'Rue Tilsitt' in the street fight scene but to my confusion no such road exists in Nice. So I took a closer look, I noticed in the scene where Albin and the spy enter the 'Hotel Des Lys' there was a street sign in the distance, this reads 'Via Andrea Vesalio', which, with the aid of Google maps I discovered is in Rome.

With further help from Google Street view I found that the 'Hotel De Lys' is actually at Via Marcello Malpighi 9 in Rome, not far from the main railway station. The hotel was and still is an insurance office - the 'Comp.Europ. di Previdenza', or CEP, whose initials you can see on the windows of the hotel as Albin and the spy walk in.

It strikes me that a lot of the outdoor scenes look Italian, and although Nice has buildings of Italian architecture I think most outdoor scenes are actually in Rome. The interiors of this film and the original La Cage Aux Folles were shot in Rome's DEAR Studios at Via Ettore Romagnoli 30.

The only scenes which were definitely shot in Nice were (I think):

1. The two scenes outside the Casino Ruhl (right at the start of the film and when Albin is in the car when the bomb explodes), which still exists at 1 Promenade des Anglais.

2. The scene at the hotel terrace where Albin is dressed as a woman and is picked up by the spy, this is at the famous Hotel Negresco, at 37 Promenade des Anglais.

3. When Albin goes into the Roi Du Bleu shop to buy workman's clothes, this shop still existed up until a couple of years ago but is now the Fenocchio ice cream parlour at 28 Boulevard Jean Jaurès.

4. The scene at the Italian/French border appears to be at the authentic location.

Also the two railway stations 'Val Di Sasso' and 'San Fermo Scalo' (seen at the beginning and end of Albin's train journey where he loses his wig out of the window) don't seem to exist. Perhaps they were stations near Rome given fake names?

So the majority of the scenes set in Nice seems to have been shot in Rome, often with fake French road names covering up the real Italian street names. One giveaway is street furniture such as school warning signs etc being Italian rather than French. The continuity is excellent though, for instance it would be difficult to tell that Albin and the spy's short taxi journey from the terrace to the hotel was filmed in two different countries!