Yes. To upload a new .mp3 file for a submitted song, please go to your "My Songs" page at https://www.broadjam.com/artists/songs.php and click the "re-upload" button next to the song. Once activated, your new version will stream for the Opportunity Provider immediately.
Warning: do not delete your song. This will remove it from any submissions you have previously made to Music Licensing Opportunities, Contests, and Pro Reviewers.