There's a story I quite like from an obituary of Peter Berger, but I'm wondering if there's any truth to it (if not in the conclusion then perhaps in the facts):
"Zita had a right to be buried in the Imperial Crypt in Vienna, and the Austrian authorities agreed to that on the condition that the Hapsburgs paid all the expenses. The funeral, held on April 1, was huge—more than 6,000 mourners attended, including a personal representative of the Pope.
But the clerics discovered a problem as they anticipated the funeral service. Zita’s titles, as befitting an Empire that had married more than fought its way into expansionary greatness over the centuries, were very lengthy—and according to the order of the imperial funeral, all of them had to be read out loud as part of the ceremony. The titles included her own royal identity in the House of Parma and ended, two and a half pages later, according to the official list, with: “and the Duchess of Auschwitz.”
Should the officiating clerics say that, given the acquired sensitivities of that place name? They fell silent for several moments. And then, as though at once, they all knew and agreed: Yes, “Duchess of Auschwitz” should be said, and they all knew why: Because if the Hapsburg Empire had not been destroyed, there never would have been a death camp in that place."
A bit late but yes, Habsburg rulers traditionally held the title of the Duke/Duchess of Auschwitz (Oświęcim).
The Duchy of Auschwitz had existed since 1315 when it was created as part of the division of the Duchy of Teschen and was originally ruled by the dynasty of the Sileasian Piasts who sold it to Poland in 1457. As part of the first division of Poland between Prussia, Russia and Austria it became part of the Austrian territories and was incorporated into the administration of Austrian Galicia. The title of Duke/Duchess of Auschwitz was first officially listed within the larger title of Maria Theresia and continued from then on to be part of the official full title of the Habsbrug Crown while the territory itself became part of the German Bund in 1818 and subsequently of the Polish Republic in 1918.
The full title of the Habsburg Emperor in 1914 thusly was:
His Imperial and Royal Apostolic Majesty,
By the Grace of God Emperor of Austria,
King of Hungary and Bohemia, Dalmatia, Croatia, Slavonia, Galicia, Lodomeria and Illyria;
King of Jerusalem, etc.;
Archduke of Austria;
Grand Duke of Tuscany and Cracow;
Duke of Lorraine, Salzburg, Styria, Carinthia, Carniola and Bukovina;
Grand Prince of Transylvania, Margrave of Moravia;
Duke of Upper and Lower Silesia, of Modena, Parma, Piacenza and Guastalla, of Auschwitz and Zator, of Teschen, Friaul, Ragusa and Zara;
Princely Count of Habsburg and Tyrol, of Kyburg, Gorizia and Gradisca;
Prince of Trent and Brixen;
Margrave of Upper and Lower Lusatia and in Istria;
Count of Hohenems, Feldkirch, Bregenz, Sonnenberg etc.;
Lord of Trieste, of Cattaro and on the Windic March;
Grand Voivode of the Voivodeship of Serbia etc., etc.
Correspondingly these titles were also held by Zita as the last Empress and since Zita had never renounced her claims on Austria (thus making her state burial in 1989 in my opinion an outrage) she was also buried with these titles.
The connection betwenn the Habsbrug rule and the later history of the town of Oświęcim, especially the Auschwitz camp, is also apparent in the fact that the first installations of the camp, Auschwitz I Stammlager, were build in a Habsburg military installation that had fallen out of use and had originally been build under Maria Theresia in 1756.