I can't offer many details on this, because the mists of time have descended, 
but I had an issue similar to this when I was moving all data off a file-based, 
deduplicated pool to a VTL-based pool. After all the data had apparently been 
moved to the VTL there were still volumes left with something on them.  I 
opened a support case. TSM Support was able to confirm they were not data when 
I gave them the output of some select statements against DB2 tables that they 
provided. In the end, Support and I concluded that the remaining files on the 
File pool were orphan chunks from the deduplication process. After that I 
deleted the volumes because I need the LDEVs back for another purpose.

Best wishes,
Keith Arbogast
Indiana University