Mike I think this is rosemary (Rosmarinus officinalis) can you pick a bit and confirm whether or not it is rosemary. This is the first time I have heard of it becoming self established in Canberra
The one in my garden is in full flower. I cannot think what else it can be. Do the leaves smell like rosemary? I do not know of anything else that does.
It smells rosemary and the flowers match rosemary from the garden centre. There are plantings of two varieties of rosemary in open space over a kilometre away, and maybe more in backyards.