Somone discovered a rather strange method of restoring 1.9 backups in which files were no longer tagged as legacy and the course used the new file system. Had to have a version 2.3.lowerthanhighest (possibly a 2.2 would work).
Bascially it went like this ... create a blank course in the 2.3. Then restore into the course just created a 1.9 backup into the same course.
Have watched the process via command line and moodle first created a temp directory where it un-zipped the 1.9 backup, then ran through a routine to rebuild the backup directories/files in another temp directory, but this time it had a moodle_backup.xml (rather than a moodle.xml file) which was the road map to restoring the course.
This was the ONLY method to restore 1.9's to 2.x without legacy. Yes, a pain in the ....!
For one school that had over 200 courses, teachers were given the option of starting over or having their 1.9 course 'migrated' through a 2.3.x and then backed up, then restored to the higher version. It took about 3 weeks time.
'spirit of sharing', Ken