Do you know who owns the attacking dog and who the victim is otherwise the council won't do much with a 3rd party report unless the victim comes forward to lodge a complaint? Personally I think the choice to report lays with the victim and it may just be the incident to take the owner of the offending dog to the next level of responsibilty with a 2nd chance.........having said that, if the dog is "already" declared dangerous it doesn't appear that the responsibility that comes with the containment of a declared dog is sinking in?.