I used to deal with DOTARS on a weekly basis. Sure it was regarding Diesel Engines for Trucks, but similar processes i imagine were in place.
It took anywhere from a year to a just a few weeks to have them pass. The ones that took a year were, where legal teams were involved. Mainly because DOTARS do not like dealing with Carbon Credits. Most were passed within 1-2 months.
I do not understand the laws in their entirety regarding on road testing... but believe me when i say i have driven prototypes with trade plates legitimently. These were one off's that have since had a few changes and then proceeded to production.
I assume that Nissan Australia will be conducting some testing of their own (to fine tune suspension etc for our sub-standard roads) and i have also heard of more than 3 R35's getting about.
Either way, it's a great looking car, it's performance is un-questionable, i'd love to see one on the street, talk to the owner and look under the hood and more to the point, i want one.