Nope. Front Page backup from 1.9 will not work in 2 ... period.
When restoring 1.9 backups users will not come across (no users will be enrolled or assigned roles in courses) and one will get *stuck* in 'legacy'. There used to be a way to start a 2 course, then restore a 1.9 backup and avoid legacy files, but appears that ability has been removed now.
None, to this date, have said how long 'legacy' will be supported in Moodle 2. So if restoring 1.9 backups one has some work still to do with re-uploading files and then relinking them in the converted 2 course. Once that is done, and only after it's done, can one turn off Legacy at the course level. After all courses have been re-linked, then one can turn off Legacy at the site level.
While you are doing that, filedir will grow.
'spirit of sharing', Ken