I had one of those red-e deal tickets MEL-SYD ($50?) late last year. The flight was a 747-400 and I got seated in the business section on the main deck. May have been because I am emerald status with AA. I asked the CSM about it and he said that they seat business class either in the first class cabin or upstairs. Only problem with these internal flights is that you cannot pre-reserve seats, so it is either luck of the draw or turning up early and requesting a specific seat.