Nothing that I know of. Only thing that comes to my mind is the Imperial Station, a station built for the emperor that was never used. Yes, and one big tram station was never finished. It was built for several tram lines passing the old downtown area underground, but this underground passage was never built. The station is now terminus of no less than 7 tram lines (37, 38, 40, 41, 42, 43, 44).
U1 is one of the more recent lines, being mostly underground. Highest suicide rate. U2 is an extended underground tram line and pretty useless. U3 is again a newly planned line. U4 and U6 used to be urban train lines until 1976 (U4) and 1989 (U6), U4 underground and in galleries along the Vienna river and the U6, probably the most beautiful line, mostly on bridges up above the streets, all the bridges and stations have been designed by Otto Wagner, a very famous architect in the 1890ies and the early 20th century.

[Linked Image from dominikanerinnen.at]

And then we still have a few real urban train lines, the elevated train or "Schnellbahn". They belong to the Austrian Railways and use real train cars instead of tram cars. Very very comfortable, but you have to deal with 15 min intervals instead of 2.5-10 minutes on other lines.
In spite of the efforts of many politicians Vienna still has a very effective public transportation system.