I followed the link Enerson gave, and on that page there is a link to "A Guide to Using Travelers Cheques" (sic).In this 2-page Guide there is a list of countries, which does not list Austria, but it does say "EUROZONE COUNTRIES: Travelers Cheques acceptance in the Eurozone is very limited away from airport locations. This document indicates partners who, at the time of publishing, were known to be encashing Travelers Cheques for non-account holders. You are strongly advised to use the TC Locator americanexpress.com/useTC to confirm the latest position".
They are selling the things, and even they admit they are difficult to cash.
The "TC Locator " on the web page does list the following locations in Vienna whch allegedly accept them:
1. Interchange Austria GmbH    Stephansplatz 9    Vienna, A-1010
    2. ChangeGroup    Singerstrasse 1a    Vienna, 1010
    3. Erste Bank    WohnbauCenter Wien, Brandstätte 7--9    Wien, 1010
    4. ChangeGroup    c/o Laks, Kärntnerstrasse 16    Vienna, 1010
    5. Erste Bank    Graben branch, Graben 21    Wien, 1010
    6. Erste Bank    Kärntner Straße branch, Kärntner Straße 45    Wien, 1010
    7. ChangeGroup    c/o Sacher Hotel, Kärntnerstrasse 38    Vienna, 1010
    8. Erste Bank    Wien-Mitte branch, Landstraßer Hauptstrasse 1b    Wien, 1030
    9. Erste Bank    Ringturm branch, Schottenring 30    Wien, 1010
    10. Erste Bank    wohn²Center Wien branch, Praterstraße 38    Wien, 1020