How to handle 3-party code with unknown/implicit license?

As logged under HIVE-28155, there is some code in Hive that has a copyright notice pertaining to a BSD license but I couldn't track the actual provenance of the file to know the exact license that applies to this file. 

 * Copyright 1988-1992 Regents of the University of California
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that the above copyright
 * notice appear in all copies.  The University of California
 * makes no representations about the suitability of this
 * software for any purpose.  It is provided "as is" without
 * express or implied warranty.

The notice implies a BSD-3 license but given that the copyright dates back to 1992 it seems plausible to be under BSD-4 since the advertising clause was removed on 1999.

Can/Should we make assumptions about which BSD license applies to the file by relying on the copyright notice?

What should we put in the main LICENSE file of the Hive source? Should we copy the copyright header from the file or do something else?