Trenitalia is the primary train operator in Italy. A subsidiary of Ferrovie dello Stato Italiane, itself owned by the Italian government, it was established in 2000 following a European Union directive on the deregulation of rail transport. So basically its owned by the Italian government through its own company.
I am no expert on the 4th Railway package, having only read one article on it. I think its to harmonise safety standards etc which is not a bad thing. Even if different companies have to bid for franchises, these companies can be state owned or a mix of state- private. Its ironic that many of our private train companies are actually owned by European state enterprises, so our high fares and taxpayer subsidies to our rail services are going towards us funding the cheaper services enjoyed on the continent. Instead of blanket renationalisation, there is also the option of having community owned transport systems in a local area, as is the case for some bus companies, and I believe one rail line, whereby a private company does not run for shareholder profits but all profits are reinvested in the services.