As far as I know, you can't. It is signed off to certificate/key on the box you took the dump from. You can only restore it to the same server (though you could probably restore it via the shell to the new server). We haven't looked very closely at the backup feature after some initial problems with it, so you might have more luck asking on the Plesk forum about this.
It has to be done by the admin on commandline and has to be remapped to the new servers IP's. Moving from Plesk 7.0 to 7.0.2 to 7.0.5 are not issues. Going to 7.1 would be an issue.
For example, execute psarestore -f /root/psa_backup/client_backup --single-domain-mode --domain-name=client.domain.com --domain-ip=188.8.131.52 --clien-login=client to restore a domain named 'client.domain.com' from the client dump-file /root/psa_backup/client_backup for the client with login name 'client' at the IP address '184.108.40.206'.
Wow, there seem to be some other people with the same issue in the plesk forums. That is one I have not run into myself and I do plesk contract work for many datacenters as well as custom plesk work. Here is a link to the 2 threads ind plesks forums.