I doubt you could do it and restore all logs and such as easily. But to restore the site and database would take no time in ssh. Just make the new user, the db, subdomains and such in vhcs. Then wget or ftp the cpanel backup over, unzip it and restore www files where they go and import your sql.
Could be done in minutes. Im not too familiar with vhcs but I have moved accounts between plesk, directadmin, and cpanel and restoring www files and dbs is fairly easy. I doubt there is any sure fire conversion script. Looks like something you have to do manually