Seems okay for A. littoralis for me (keyed fairly well in VicFlora). Obviously if it is not a local species it might be harder to eliminate other possibilities but I don't see why it could not be naturally occuring or a local planting.
It won't be naturally occuring A.littoralis has a very limited distribution in the ACT, it isn't A. verticillata or A.luehmannii. Littoralis is commonly planted & I suspect the most likely.