Mate, don't get me started on environmental weeds!
Blackberries are only one of MANY. The list includes broom (both "English" and "Canary" types), gorse, spanish heath, african boneseed, lupin, tree lucerne, foxglove, ragwort, morning glory, several types of thistle, crack willow, and even some types of Australian plants such as the Cape Leeuwin and Cootamundra wattles. Oh, and radiata pine: have you noticed how that spreads itself all through the bush?
Every one of them is detrimental to wildlife - either by ruining its habitat, or by direct toxic effects on the animals/birds themselves.
Every one is rife in various areas of the state, often on land that is either state or a local council's responsibility. They also occur on private land. A council can order you, as a landowner, to get rid of various ones from your land. But, as you suggest, invariably councils and state do NOTHING about cleaning up their own act.
My wife and I regularly and constantly draw our local council's attention to the issue, and to outbreaks of all sorts as we come across them. The local NRM officer knows us well. As and when they find a bit of money, some of the issues get addressed, a little. The trouble is, the problem is already way bigger than anyone's budget can cope with. I don't know what the answer is...