I managed to find out the time of the concert: 16:00 in the afternoon. As you said that the girls are landing at 14:00, I think it´s a bit too tight to get to the concert. They might be able to do it if they head straight there instead of going to the hotel first, but I don´t know. Vienna is a fast airport to get out, if you are travelling from within the EU, but as they will be on a transcontinental flight, I don´t know how hard will the security controls.

If they want to try it, they should get a taxi and asked him (or her, there are quite a few lady drivers in Vienna) to get them ASAP to the Musikverein (the concert is held in the same building as the New Year´s Concert). The doors open at 15:30. If you tell me the name of the hotel, I´ll be able to find out if they could try to check in there first, leave the suitcases, and run to the concert. http://makeashorterlink.com/?Z21D61DF2

If they decide that they cannot make it, and if they are staying that Sunday, they could try to go to the Mass at the Hofburg (but they had to wake up pretty early).

Kind regards, Covadonga Bilbao - Spain