Where there are 'economies of scale' (and the evidence is that there are very few), councils can (and do) work together to share resources or to outsource functions to other councils.
Where there are no economies of scale (most local government activities, according to the evidence), all amalgamation achieves is a loss of community identity - and the cost of changing everything from letterheads and signs to computer systems.
The loss of community identity and the lack of synergy in proposed amalgamations is epitomised by the proposed merger of Queanbeyan and Palerang Councils which have "fundamentally different demographics", with Palerang being largely a rural council, dealing with or delivering services into the farming community, small rural villages and towns, whereas Queanbeyan is essentially an urban council (below right).
Good luck to the NSW communities that are resisting the pressure from the NSW Government. I can understand why some have chosen to submit a Plan B, as many Councils did here in Western Australia, but I'm not sure this is really the way to go as the Plan B implies an acceptance of amalgamations that are not wanted by these councils or their communities.