score:7
I contacted the Australian Embassy myself and explained what I needed to do in Australia, to confirm whether the ETA is correct or not. I was informed that in order to undertake temporary work of this nature (carrying out an experiment using a large amount of very specific equipment we bring ourselves, and not just using a computer), I was required to have a Temporary Work (subclass 400) visa.
My employer did not agree with this, but I went with the advice of the immigration official, so as not to risk any problems. Keep in mind that this option is significantly more expensive than the ETA, especially if you require translations.
NB: Probably I could have gone to Australia and been let in, but that would require lying, which I would not recommend. But according to the official I spoke with, given the speciality of the work being done, the correct visa is the 400.
Upvote:7
The right way to sort this out is to ask your employer. It's very likely they have done this before, and they will know all sorts of things which we can't, such as whether it is an official government to government visit. They should also give you help with your visa if you need one, and should provide you with a letter stating the nature of your visit.
Per diem are not considered pay, since they are supposed to be recompense for expenses you have incurred.