If you dig into the data files, you'll find there is now a "hidden resources italy". All the provinces on the Italian peninsula have this resource, and yes, that includes Mediolanium and Patavium. Since no units require that resource to be built, I assume it's there for the Reforms trigger. There's also a "hidden resources rome", but it's in there for the First Cohorts. They can now be built at a barracks, one size greater than the regular legionary cohort could be, but only in Rome.