Have you tried boards. cruise critic you will probably have more luck there....Love Brilliance though ....Neil Dow.
We used the train service last year (although not going on your cruise) but it might be worth you trying this.
It's very efficient - not like ours.
We had a brilliant time on the QM2 and went on the official coach trip to Rome from Civitavecchia; we later found out that the Rome Express leaves the Dockside for Rome for about £9-50 retur.
We have done a cruise to Civitavecchia and it more economical to book from the ship and if you do go on your own and don't return to the ship on time it will depart without you.hope this helps.
Go to the railway station about 10 minutes from the dock. There are plenty of trains there and back and it takes you to the heart of Rome. The ticket also gets you on the Metro and Buses free. Have a good trip.
We have recently returned from Rome and would recommend the train, it is a lot cheaper, quicker and very efficient ( much better than uk trains ).It leaves from the main station in Rome and the staion in Civitavecchia is not far from the port, there are always taxis waiting just outside. You only need to get a taxi the short distance to the ship. If you look at the boards on cruise critic.com you will find a link to the Italian train website in English, where you can put in the date you require and it will give you the timetable. Good luck.
The train is definitely the best bet and cheap, it runs from Fuimicino airport or the centre of Rome. There are organised buses from Ciampino which take you into Rome centre. The walk to the port gates from the train station in Civitivecchia is literally 10 mins, when you come out of the station turn right and walk along the sea front with the sea on your left and you will arrive at the port gates where I am sure there will be transport laid on to the ship as the dock is enormous.
Whilst on a recent cruise we landed at Civitavecchia and took the train to Rome, getting off at St Peter's. The fare was 8 euros return. Very clean trains and a good service. Staff are very good on train and at stations.I'm sure others will recomend this.