The G&O Garden Railroad has used Atlas 3-rail track outdoors for 10 years. It has held up very well in direct sunlight. The G&O is in the San Francisco Bay Area so the climate is similar to many of Australia's coastal climates. I have visited Australia 4 times.
The G&O does not use the Atlas switch machines. The display's 25 switches are thrown by hand. The Atlas switch machines are not UV resistant and they do rust in the rain.
Here is link to the G&O Story on this forum:
https://ogrforum.ogaugerr.com/.../the-gandamp-o-story
NH Joe