Interesting question:
One Friday way back in early 2001-2002 we had a user CHMOD all the files and folders in the home directory. We were alerted to the problem Monday (after 3 nights of backups had run) and proceeded to restore the home directory. TSM does not just change the permissions, it has to restore the files...the problem was that none of the files were backed up again. Back in the day (and I think they changed TSM's behavior) when UNIX permissions changed TSM would only update the permission settings in the TSM DB for the file. So restoring the files did us no good since their were no previous versions on many of the files that had the old permission settings. I never did go back and check to see if they changed the behavior. I'm pretty sure they did, but back then it was not how TSM worked.