If One looks back to the late sixties and early seventies, the Eurocontrol plan and agreement was for European international ATC centres at Maastricht, Shannon and Karlsruhre, operated by Eurocontrol. The Karlsruhre centre was built but rapidly a victim of, I believe, nationalism. The Shannon centre was an earlier victim. The Maastricht Upper Area Control Centre, somehow survived and thrived, as an example of development with international ATC cooperation. It still is. Having worked there from the opening in1972 until five years ago, and before that at the Brussels UAC from 1970 - 72, I consider it a great success. I believe we were the first for direct routings, having been 'on the phones' in Brussels coordinating with 'France', with traffic from the Dutch border sent well into France (CTL, NTS, among others), those were the days. Anyway, Eurocontrol was an innovative idea which was constrained by politics. At least, the Maastricht Centre survives... with the echoes of 'Chuggalug' and from what I have experienced, a great reputation, having spoken with many flight crews over the years.
Just my sixpenth worth. Very happy days.
zed.