Which train line is everyone using when you say "trains"? The Trenitalia website specifically says "Green Pass or equal", however Italo does not. I messaged them on Facebook asking explicitly about the CDC card. They just said Green Pass and pointed me to the https://www.dgc.gov.it/ website. I then screenshotted the specific FAQ from that website where it says United States equivalent to be accepted as a Green Pass and sent it to them. Their only response was to give them a phone call.
We just arrived in Rome today. Taking a train to Lucca in a few days and after reading all of the comments about CDC cards and trains, I asked the front desk lady at the hotel. She took our ticket info and called Italio for us. They said CDC card is acceptable. We shall see
Do you realize that you are asking some employee at Italotreno's call center if the unknown conductor working on a certain train on a certain day has read the company memo about the CDC card and if he/she will obey the law?
All they can say, obviously, is: "Sure, our company obeys the law". What else could they say? Maybe: "To tell the truth, I have no idea who will be on duty of checking green passes on that train and if he/she usually reads the instructions"?
The law is the law.
asking explicitly about the CDC card.
That's a confusing mistake. Obviously, The Italian law doesn't mention neither the CDC card nor the Canadian equivalent; it says: "Green Passes or documents issued in USA and Canada with the same specifications".