Austria lost all his mediterranean coastlines, along with Hungary, with the treaty of Versailles, and the boats were surrendered to Italy, and France.
There may be several reasons why they were not sold.
A strong one may be the resentment towards the enemy, so like with the german U-boats in "Operation deathlight" after WW2 where they examined and then sank and destroyed them, rather than putting them to use, or sell them. Some of the technical development was still secret and advanced for the time, so to whom should they be sold without giving others a key for modern technology.
Also this outlandish machinery with different system of units and all that. They would have been difficult to maintain without trained personnell and the original tools. I guess it was easier to use the ideas and build their own new boats around them, and then scrap the old ones with their secrets.
Another possibility is that the austro-hungarian boats were technologically obsolete, already in 1914. They had already also used german U-boat designs at the time, if with changes and adaptions.
http://www.wikiwand.com/en/U-27-clas...ustria-Hungary)
I admit i have not enough knowledge about the austro-hungarian fleet though, especially not when it comes to post-1918. Afaik most of the fleet was based in Trieste, and Pola, and i also have no idea where all those surface units were surrendered to.
