There is a national strike called for tomorrow, 22 June 2012, and in Rome, there will be strikes affecting all buses, trams, and some trains. I am in Rome now and have discovered that if you are planning to take a train from the city to FCO, you will be able to do so from the Termini Station or the Trastevere Station up until either 8:30 am or or 9:00 am.The trains going to Trastevere station from Orte are guaranteed to run. The other trains that usually stop at Trastevere Station are not guaranteed to run, though they may after all run.
To reach either train station, you should be able to take a bus or a tram up until 8:30 or 9:00 am.
If,overnight,yet an additional strike should be called affecting the few remaining trains to FCO, the ATAC authorities in Rome say that in place of the trains to FCO out of the Termini station, there will be buses instead. The strike seems to be in a flexible mode. If you are leaving tomorrow and are using public transportation, you might want to leave out of the Termini Station. But if you are nearer the Trastevere Station, you should try for one of two trains that will get you to FCO before the strike goes into full force: 7:50 am or 8:05 am.
Since the strike goes all day and into the evening, with only a break from 5 pm to 8 pm, you should get to Fiumicino as early as you can no matter when your flight leaves.
Also note that taxi fares to FCO from the city center rose on June 11 after a long negotiation with the city. The base price went from 40 Euros to 48 Euros--not counting charges for bags or charges for pre-7:00 am travel, which counts as night travel.
Finally, US Airways say that there is a 100 per cent change that flight # 719 to PHL will go forward on 22 June 2012, although there also is an air strike in Italy. The international flights all should go forward, I think.