Sorry Steve for continusly replay... but I'm working for testing.
I discovered a thing:
Indeed the mount works fine... the problem is the sync with media library.
I see that media library sync and update only when you add a file with cc3 file manager or FTP.
If you delete a file in the media folder and wait for the sync nothing happen, equally if you force the mediascan cron.
The only way to see changes in the media library is upload at least one file in the media folder. Only after that, any changes done in the media library (including deleted files) are synchronized.
And the the shared folder with mount works fine too... but only after adding at least one file in the normal media folder the content in shared folders are views and sync with media library.
Is it probably a bug?