Alex replied:

G'day,
number of the tracks out there get pretty wet, and even the main roads may be closed at times during winter, but by September you should be OK, but check with the local shires first.

It may just be rumour but I heard the other day that the Holland Track had had a grader down it and could now be driven in the family commodore. Like I said, it may just be rumour, but bear it in mnd, as it may not be the adventure it used to be. Cheers, Alex.