We use library-based cleaning on out L700s, with IBM T200F and T400F LTO 
drives.  It works fine, though there is very little cleaning going on.

We just enabled auto-clean in the library, loaded cleaning tapes in the 
'playpen' area and sat back.  I read that unless there are cleaning tapes 
that NetBackup can see, it will not attempt to clean the drives itself. So 
we may be getting messages in the log if the drives raise TapeAlert, but I 
don't know and don't care.

Can't say about HP or Seagate LTO drives.

William D L Brown