If you backup and then restore with the setting 'update course settings' (or is it 'overwrite course settings' - I don't have it in front of me at the moment), then the legacy course files are restored.
It is also possible, with a small modification to the backup code, to make sure that legacy course files are always restored (even when the rest of the course settings are not), but I've not got the code to hand, so I'll have to dig that out later.