A google image search of "australian pink flowered tree" gave me Lagunaria patersonii, which looks superficially very similar to your picture.

I think Sue has nailed it. "Norfolk Island Hibiscus tree" its common name though it's not a hibiscus. It is a quite attractive flowering tree but with the drawback of the seeds having irritant qualities so best not grown near walkways. Anyway now you know, you can read up. Her'e a start.

Here is a link that might be useful: info