You can set VISRETAIN variable to "1" in your "CC" drawing, all visibility, color and lintype setings will remain the same for any xref drawings you attach to it no matter what changes are made in the other drawings. If changes are made to those drwaings that you want to incorporate, the VISRETAIN can be set to "0" and the xref reloaded will now reflect the last saved layer status in those drawings (CAUTION - this includes any such settings you have previously changed and wanted to keep). VISRETAIN can then be reset to "1" in drawing "CC" to preserve these changes.