One may remember that an Iraqi general was about to be tried in Denmark on war crimes charges shortly before the war. He vanished, an event that attracted some attention at the time. This site, whose credibility I rather doubt, claims that General Nizar al-Khazraji was taken to Taszar on board a Gulfstream aircraft operated by the CIA. (Two Gulfstreams have been identified as taking part in prisoner transfers.) They also, fascinatingly, claim that the operation at Taszar was run by none other than disgraced New York cop Bernard Kerik!
German weekly Die Zeit described the scene around the base in January 2003: massive security, with an outer ring of Hungarian troops but an inner sanctum guarded by Americans. Apparently the Hungarians were informed of all the people who passed through for border control purposes, but I don't know if any physical control was carried out - in any case no-one was permitted to leave the perimeter.
It was rumoured yesterday that Le Monde was going to run a headline regarding a "little Guantanamo" at Camp Bondsteel, the US Army headquarters in Kosovo, however
What differed, presumably, was the treatment they received once they were there..
Edit: this is essentially the Le Monde story, just the person who saw the prison's likeness was Alvardo Gil Robles of the Council of Europe. He was apparently "shocked" by the resemblance but makes no mention of torture or maltreatment.