restoring an Exchange 2007 database after the server role has been uninstalled

I would have thought that it is possible to restore any mailbox database to any suitable MS Exchange Server of the same version (i.e. of the same version that the backup came from) - without having to worry about whether AD is populated.  Otherwise, what's the point of backing them up if one is only able to restore to an MS Exchange server in the same domain which retains unchanged AD structures?

I'm sure I'm probably wrong with part of this, but then your statement doesn't seem to be valid to me either.