EBSMSHSW
Normal price of Early Bird at HSW is $15 so this is only a savings of $5, but that's still pretty good for Brisbane CBD. It's at the far end, though, so if you don't want to walk that far then Little Edward St. for $14 is a better location. Sadly, it still won't help with finding a place to park in the late afternoon or evening, which is when most people want to go there anyway.
I couldn't find the T&Cs so I don't know if there's an expiry on this.
I also got a text for Brisbane Transit Centre: BTCEBSMS