See the Alitalia home page. Hope someone tries this and let's us know how it works. Might want to try in September if it goes to Tiburtina bus station, but looks like it only goes to the train stations for now.
It's not exactly on their home page, but here's a link: Alitalia bus from FCO For another bus option see Ron In Rome on Terravision bus
I've had no success purchasing through the Alitalia bus site - I wonder if anyone has been successful
The website almost sounds like the service is for groups only. Guess we will take the train (hopefully the one that gous to Tiburtina station).
It's only for groups. "This service is reserved to pre-formed groups of Alitalia passengers/customers."
Wow! Where did see that?