Well, I found a different explanation in an old ANK special catalog.
It's a local issue of provisionally postage due stamps from 1920 in Villach/Carinthia. "T" overprints are also known for Loosdorf (Lower Austria) and Strobl (Salzburg), but those "T"s are different, this is definitely the Carinthian one.
I attached a picture of the ANK page. The prices there are old (Austrian Schillings) - it says around € 1,10 for stamps and € 45,- for covers.
The only problem I have with these overprints are the stamps they are on. ANK says, that they only have been used on "Posthorn, Wappen, Allegorie" stamps, but not on Emperor Karl I. So I'm not sure, if they are forged or not.
And the CMT is Western Ukraine, Romanian Occupation. Some very interesting facts about them can be found here ->http://www.firstissues.org/ficc/det..._CMT_1.shtml