Since QANTAS switched CRS systems to amadeus, the U availability is visible for some reason to some CRS' including ITN which suses SABRE technology.

The problem with this is that the "U" class availability - along with other QF booking classes is that it is not 'updated' frequently enough from amadeus to other CRS'.

The only way is to force an entry on the CRS you are viewing, which is impossible to do through websites and only possible through actual CRS systems. That is when you will be able to see actual availability of particular flights.