*.NCZ or *.DGN, *.DWG, *.DXF files can be added as a reference under the category in References.

You do not need to have the permission to edit these files. For example, while making plan defaults can be used as a base and interference of plan and default can be prevented.

For General and Projection Tab details ... (?) 

NCZ PasswordNCZ Password is asked when an encrypted CAD file is added to the references. Reference CAD file is opened by entering the password. Whether the file is encrypted or not can be seen in this section.
Edit Layer InformationLayer menu of the CAD reference file is opened with the Edit Layer Information command. Changes (layer visibility, color, etc.) can be made from the menu opened.