I'm now done with all the Media Imports and the thing I was afraid happened, Sessions state not all Media available for Restore.
Checked some of the Sessions in original Cell and the new one, Sessions show the same Media-IDs on both Environments and Object-Info is shown on all imported Tapes.
Any Hints on what to check to find out what went wrong here? Don't really want to re-import the Catalogs all over again.