Does Google Maps iOS have voice navigation
Yes, voice navigation is available in Google Maps for Australia. 

To enable it:


Make sure you have the most-recent version of iOS. 
Make sure Notifications for the app are turned on.
In the app, after you've started the navigation, tap on the 3 vertical dots on the bottom-right of the screen
In the panel that slides up make sure Mute is Off.


Doing all this will allow you to hear the turn-by-turn navigation prompts.   Here's a Google support site with additional information.