Mate sorry for these questions - however.
Am I to understand just because you industry is worth $350m, you are allowed to flout the law & the government lets you get away with it?
And just because your vehicles are registered in a different state, you don't have to follow SA rules? (Only federally registered vehicles can do this as they are down to the lowest common denominator).
Now there are only 3 services mentioned in the Fire & Emergency Services act -SAMFS,CFS & SES, ergo private contractors are not emergency services under the meaning of the act. Now I now that there are some on defence land (federal government land is out side of state legislation -defence act) however without an MOU(or permission from the state at the time) even these resources can't operate outside of their area of responsibility unless there is a direct threat to their area & its under the direction of the government emergency services. I also know that mining & forestry have their own equipment & people - again these resources fall outside the act when they are off their patch.
Now the private sector may have the very best gear & very well trained people, however you are not emergency services! You do not have the powers of an emergency service officer or the protections the act provides. (There is more to being a government emergency service than putting water on fire, or cutting people out of cars) & when the public see Red & Blue emergency trucks they assume - quite rightly that they are government emergency service teams.
Now maybe the legislation should be changed to cover private contractors & their operations, But until that happens you are just another resource we can call on & use in certain circumstances. So get used to it! Defence has had the same problem since 1907! (refer to discussions on defence aid to civil powers & the Newcastle earthquake). Interestingly under the state act if your truck was at a scene & I was the first emergency service officer the job, I can direct your crew to do whatever(as long as its safe) including to standdown!
Finally I still think its great you guys are considering helping out, just remember you are contractors with weird water tankers - not an emergency service
cheers