Peter, here in Germany, it was repeatedly announced in TV/Radio that these vests are compulsory (? correct word ?) in Italy. I also can receive RAI TRE (italian TV program), and there it was also mentioned repeatedly - I watch it sometimes as I try to learn a bit of Italian ...

I did not find pages in English, but here are two pages in German (maybe you can use some automatic translation like Babelfish or similar):
http://www.landesverkehrswacht.de/lvw/ratgeber/ratgeber_299.html
http://www.europaeischesverbraucherzentrum.de/UNIQ109306799718076534/doc663A.html