I can't see the location until this is formally identified but from your other photos it is near the Mugga quarry. There is a huge population on the gravel heaps nearby and the weed has gone down into the Mugga Mugga Nature Reserve as well. I remove isolated plants but this area needs major work.
Centranthus ruber. There might be a glitch in the system. I selected Centranthus ruber then added a comment, but the suggestion ended up as inconclusive and I haven't been able to change it.
this is just across the dirt track from the quarry, a little further south of http://canberranaturemap.org/Community/Sightings/Details/1974489 It is quite a large infestation