I agree, grinder, try mtx. There is a standard set of SCSI commands for handling changers, which are likely whatever your backup system is using anyway. With a quick google search, I see that it can use a SCSI LVD/SE, SCSI HVD, or FC interface. Even if you have the FC version, it should accept commands and inquiries from mtx.

Too lazy to log in,
hattmoward =)

Oh also, shameless backup plug: Bacula keeps your servers smelling fresh.