Back closer to topic...
Euro 4 spec was set intending DPFs to be fitted. Most manufacturers managed to meet Euro 4 with tuning and an oxy-cat - so no DPF.
So most Euro 4 spec vehicles do not have a DPF - just an oxy-cat.
Euro 5/6 Introduced a particle number concentration limit, to force all manufacturers to fit a DPF.
The Australian automotive industry has said that Euro 5/6 is too hard to meet at present, and negotiated a gradual phase-in of 5/6 until 2018 (passenger vehicles), with the particle number concentration limit the last
item to be introduced.
Imported vehicles may or may not have the DPF removed for the Australian market. Most Australian made diesels will not yet have a DPF.
As for spinifex and DPFs... On tracks like the CSR, most of the burnt out vehicles littered along the tracks are petrols. Some of these presumably due to spinifex fires. Modern diesels without DPFs could also have spinifex collect around the turbo or oxy-cat. If you are driving in tall grass or spinifex in any (modern) vehicle you would need to stop and clean the vehicle regularly.

