When there's miles of perimeter fence, some spots will be weaker than others from a security standpoint.
High value shipments typically rely upon "security by obscurity" to the great profit of certain moles. I would not be surprised if the spending habits of employees in the various concerns will be carefully monitored. Somebody may decide to take early retirement and not return from vacation in Brazil
Prevention of this kind of robbery requires an armed motorised escort until cleared for takeoff and the same at the end of the landing run.
But if the armed escort disables the robbers' vehicles, you end up with a bunch of seriously armed men running around the tarmac with potentially thousands of innocent people about-- potentially very messy.
The airport authorities might prefer these folks vacate the premises pronto and let the police do their work.