I don't believe the music has actually been released, so short of cracking the game and extracting the actual music files from the cd, you will have to wait for them to release the music. Even then, I'm not certain the piece's name would be included in the file name.

FYI, the released OST are Before Meteor (with all the music from FFXIV 1.0) and Sounds of Eorzea (only includes the theme music for the towns and the adjoining fields). Those are still great soundtracks, but they don't have the Odin battle theme.