Seems this expired deal has been renewed with the reduced annual fee of $150 for existing Westpac customers in the first year ($295 thereafter) and a $75 annual Qantas rewards program fee.
Earn 90,000 bonus points with $6,000 spend on eligible purchases within 120 days of approval, with an additional 30,000 bonus points after the first eligible purchase during the second year.
Not applicable if you have held an Altitude Platinum or Altitude Black card with Altitude Rewards, Qantas or Velocity in the last 24 months.
For me the earliest was 3 months (confirmed for myself). I'm not sure if there have been any records/reports of any earlier. Although technically (according to T&C's) you should be able to as long as you don't have any other Citi products.