SQL 2005 Full Recovery Mode Point in Time Restore w/out Backup
Not just using the transaction log, no. It records redo, but not undo, so you can only roll forwards from a point in time, which is the time of a backup. It may be possible to replay the entire log from the start on a blank database, but I don't know you'd "tell" SQL Server that you wanted to do that, even creating a database "for load" probably wouldn't allow it...