It would not be possible to utilize an Ensim backup for the purposes of migrating to cPanel. The cPanel migration tools explicitly require a live and working Ensim install to grab current data and configurations for an Ensim account.
As to why migrating from Ensim backups isn't supported, a discussion on a similar topic (restoring from Plesk Backups) can be found here: http://forums.cpanel.net/f5/plesk-cpanel-migration-157105.html#post670978
Essentially, the added potential for differences/conflicts/problems is substantially compounded and make such a process unrealistic. If at all possible, I would advise restoring the Ensim backup to an Ensim machine and then migrating accordingly from there.
If you're able to get the Ensim backup restored to a working Ensim server, definitely take advantage of our Free Migration Service cPanel Migration Services - cPanel Inc.