Yes i did it a few times. But it's a different procedure if you restore it to the same server or to a different one with another IP address.
One thing i'm not sure about is if you extract tar files from an old vicibox 3 server to a fresh installed vicibox 6 server if it will work right away. For instance if you install the new server do you have to do the vicidial express or vicidial-install command yes or no? I always do it (never tried without that step) and if you do you have to take care you install asterisk 1.4 (i think?) and not asterisk 1.8 or your restore won't work. We also had problems with MySQL when restoring because it was a different version. My colleague had to do a lot of troubleshooting, it wasn't as simple as the steps above but maybe we also messed up along the way.
It depends on your starting situation and where you want to end up.
One more useful thing. If you want to move over your backup files from an old server to a new server i use this command to copy over the files"
nohup scp -rpC /var/log/astguiclient/archive/yourbackupfile_ALL_4.tar.gz root@yourserverip:/
Do this for each of the backup files and they will be copied to the root of the other server.
For copying over recordings you can't use the above command if there are many files, you'll get the error ' too many arguments' . I then install a program called Unison and use this command:
cd /var/spool/asterisk/monitorDONE
unison MP3
ssh://yourserverip//var/spool/asterisk/monitorDONE/MP3To get mysql to work after moving stuff over you can try the mysql_upgrade command
You will have to use the server update ip script, server rebuild conf files, check if NTP is configured properly, update the server ip address in the server admin page, update audio store server and finally update your DNS records to point to your new server.