There are things I'm sure you could do - for example, opening a file or folder with FILE_FLAG_BACKUP_SEMANTICS lets you completely bypass ACLs, assuming you have the SE_BACKUP permissions (Administrators and other members of the "Backup Operators" security group).
One other possibility, that in fact sounds quite likely from your description: are you sure that the apps aren't *running* in the background? 8.1 makes apps suspend, not close, by default even if you do the swipe-to-bottom-of-screen gesture. Obviously, if the files are locked, you won't be able to edit them. That should give you a different error, but you never actually said what error you're getting.