The RAAF is replacing the current BBJs with new BBJ's based on the B737Max8

The Royal Australian Air Force will complete a comprehensive recapitalisation of the Special Purpose Aircraft (SPA) fleet next year with the delivery of new aircraft to Canberra-based No.34 Squadron. Through the program, Defence has leased two Boeing 737 MAX 8 Business Jets (BBJ) to replace both 737 Next Generation BBJs. The replacement of the BBJs will mark the renewal of the entire fleet, with the three Challenger CL-604s replaced by a like number of Dassault Falcon 7Xs in 2019.
No.34 Squadron’s two existing BBJs were acquired in 2002 and are starting to show their age. In recent years, according to Defence, the current fleet has failed to meet scheduled annual flight hours due to maintenance and associated readiness issues. These issues have also manifested in a very public manner. In 2020, during the height of the COVID-19 pandemic, a BBJ carrying then-Prime Minister Scott Morrison broke down in Cairns forcing a critical National Cabinet meeting to be delayed.
Rather than extend the current lease beyond 2024 the former government approved the acquisition of two new aircraft in December 2021. In February 2022 National Australia Bank (NAB) was awarded a $372 million contract, excluding sustainment, to provide the Commonwealth with two Boeing 737 MAX 8 aircraft through 2036. It’s not clear if NAB has elected to purchase the aircraft outright and provide them to Defence, or if they’re being dry leased from another company.
ADM asked Defence several questions about the aircraft including if they will be covered by the existing SPA maintenance contract with Northrop Grumman Australia, and if Defence had considered non-Boeing options for the requirement. ADM also asked about the ownership structure of the aircraft themselves.

Defence declined to answer these basic questions, however, in a statement a spokesperson said: “The leases for the two current Royal Australian Air Force (RAAF) Boeing Business Jet (BBJ) aircraft expire in 2024. Government approval to replace these aircraft with two new 737-8 BBJs was provided in December 2021 with delivery of the two aircraft scheduled for 2024.”

https://www.australiandefence.com.au/defenc...vered-next-year

The two aircraft currently carry the reg Both N786BJ and N787BJ

Boeing 737 -8 BBJ 67959 8532 A62-001 Royal Australian Air Force at BSL 29feb24 prior delivery ex N786BJ

Note: it looks like the aircraft will be using A62-001 & A62-002