There is solid evidence of criminal activity among airport security and baggage handlers. It makes sense to send dope from Brisbane to Sydney because Sydney is the biggest city and the biggest market.
Sending by road risks detection. Baggage handlers enjoy safe access to airport..no checks on what they carry in or out.
Baggage handler puts dope in zippered compartment on boogie board, nice and obvious for easy removal in Sydney.
Now this system has a fatal flaw, if the Sydney handler fails to collect the stash...oops!
Reasons for failure to collect could include...big cocaine shipment on same day (fact), undercover agent in Sydney airport has blown his cover (fact).
If the handler in Sydney had any suspicion that he was being watched then he would simply let the package go through.
The defence team has asked repeatedly for forensic testing of the bag and contents. Just one fingerprint belonging to a baggage handler would have been conclusive proof.