with the final file (which should be playable by most media players) you can just copy it to your usb stick and watch it in xmb (correct me if i'm wrong).
i think the ps3-part of the hdd is XMB managed - so you can only copy something onto it via the XMB but i have not yet linux on my ps3 - maybe you can just mount the ps3-part and copy things into it.
i think you have first to bring the backup in a ps3-playable format. if you just dump the content from the bd it will be some encrypted data. in the howto on the first page he first dumps it on the ps3 then encrypts it on the pc