Without stepping on this thread, here is what I understand to be the status of metal parts in company hands:
Sony Music - Holds Victor parts + some HMV; disposal of Columbia, et al. metal may be related to the closure of the Bridgeport plant (cf. AFR Lawrence papers at LC)
Former EMI - Holds primarily classical parts - most pop metal and most of Columbia was destroyed during World War II. Also had virgin pressings of pop material. Vault inventory exists. Note: for metal trasnferred for the Great Recordings reissues of the 1950s, metals were destroyed;
Former EMI-France - Holds selected metal parts, primarily 12 inch classical. An inventory was made in 2005;
Universal Music France - Donated metal parts to the Bibliotheque nationale - most consist of 45/LP metal, though the donation did include on previously unknown Edith Piaf side;
Former Electrola - All metal destroyed during World War II - company solicited metals from affiliates to restore catalog after 1945;
Deutsche Grammophon - Holds ca. 5K parts pre-1914 from the 'Gramophone' catalog - many DG/Grammophon electrical metals survived in the pressing plant but were destroyed thereafter;
Warner-Teldec - 78 Telefunken metals currently survive - other metals survive in Japan;
Nippon Columbia - Some metals survive.
A further note: Because Columbia 78 metal work after ca. 1939, and at Capitol and Decca, were recorded from lacquer session masters, the lacquers represent the original recordings and (hopefully!!) are still being preserved.
P.S. I don't believe the Universal deal with LC set a precedent for future donations ...