our hiking shoes were checked each time. they thanked us for having clean shoes, I have always gave them a scrub before heading there to make our life as easy as possible getting through the biosecurity.
They checked our tent, one jsut a look at the desk, the other time they took it in back and unrolled it to give it a good look.
if they don’t like how clean they are they will get fumigated/taken care of.
I would expect the same for bikes if you wanted the expense of traveling with them there.
We rented, but also had a small car so if we had brought bikes we would have needed something a bit larger too.
Yes things can still slip through, but they are pretty on top of it from what I have seen.