Originally Posted by
AlicorporateUK
How odd... All it says on the website is that, in order to book a seat on the bus, you must have an AZ ticket (I'm not entirely sure if it does work with code-share flights)

I am not on a code share - have an AZ flight number. Just got off the phone with Alitalia and they indicated there is a problem with the web site.
I also tried to book a train trip on the TrenItalia web site from Rome to Citavecchia with no success. Although they don't indicate, I deduced you can only book a week in advance.
A lot of fun dealing with these Italian companies.