I suspect this is Acacia pravissima.This has hairless to slightly hairy branchlets, angled towards the tips. Acacia vestita is doubtfully naturalised in the ACT. Its branchlets are cylindrical and densely hairy. I cannot tell from the photo which it is.
Betty, is the extra photo more useful? If not, I will get another. I thought it was a pendulous A. pravissima too but when I got close it was quite different from the A. pravissima in my garden. Isaacs Ridge has a number of non-local acacias and a number of plants listed as 'doubtfully naturalised'.
We need a good closeup of a leaf to see the venation and whether it is hairy or not. A vestita has leaves that are hairy, at least on the margins, and a single prominent midvein. A pravissima is usually hairless and has 2 longitudinal veins, one more obvious than the other. Also a closeup of a branchlet tip to check whether it is angled and hairless or sparsely hairy (A. pravissima), or cylindrical and hairy (A. vestita),
I have added a closeup of the leaves (Feb 2015) and a seedpod. Should I add a photo of the shrub in flower as a separate sighting because it will be a different date?