I haven't used virtuozzo in a long time and I do not have any virtualized machine at hand right now, but I think this should be as normal as a OpenVZ migration or any other Linux migration.
If you can get your hands on a backup, just inspect it and if it is a tar-ball with the root fs in it, you're good to go.
Otherwise, it'll be a little bit harder, but still doable:
1) Stop all services but SSH
2) rsync your / from the VM out to another host (as root on the host and guest to get the permissions right with -n flag)
3) tar the files there
