NSW Govt book through "in contract" Carlson WagonLits. QB Travel used to have contract (and IMHO, provided a vastly superior service - of course forgetting who got most of the business). All air travel MUST go through CWT as the "in contract" supplier. It is a serious breach to privately arrange air travel when paid for by the Govt (or even to use a corp card for the purchase).
BTW, full Y fares are about 2/3 to 3/4 of the same fare fare on the QF web site. That's the power of contracts and the reason why all travel must be booked through the contracted agent.