As I understand it, the government fares are often a sub-bucket inside the various fare classes, so you may have some government fares in "Y", some in "W" and some in "V". The contracted travel agency (Carlson Wagonlit, SATO, whatever) can see what government fares are left at any time, so you may see "Y9" showing even though there are no more "Y-government" seats available in that bucket. At least that's the way it seems to work on international flights; I've found availability in a class but the travel agent will say there are no government seats left in that class.