Pre-covid it was a very straight forward and quick visa processing.
Right now I doubt you’ll be able to get back. Bridging visa B is given for 3 months and currently only australian citizens or permanent residents are allowed to enter. If you don’t get a PR visa before is expired and the border is still closed, it’s very unlikely you can get back.
This is the issue of many temporary visa holders stranded overseas.
Australians citizens themselves have to get a permit that allow them to travel overseas as the government don’t want them back if they are traveling for holiday and then bringing the virus to the country.
So, It’s up to you to take the risk.