We have a WSUS in a internal environnement without internet access and without a front WSUS. We installed WSUS in a LAB with internet access. We approved and declined all the updates. We have done this procedure : http://nathanwinters.blogspot.com/2006/01/how-to-migrate-content-and-approval.html
This works fine. But, the approved and declined updates doesn't show up in the new WSUS. They are all classified into All updates.