The wbadmin command replaces the ntbackup command that was released with previous versions of Windows.
You cannot recover backups that you created with ntbackup by using wbadmin. However, a version of ntbackup is available as a download for Windows Server 2008, Windows Vista, Windows Server 2008 R2, or Windows 7 users who want to recover backups that they created using ntbackup. This downloadable version of ntbackup enables you to perform recoveries only of legacy backups.
Both the backups differ in structure , WBA does a image file type backup and a block level bckup , hence the incompatibility .
Good Luck !