(a) That's not right. Different High Court judges have responded differently to the question of reducing damages because of other benefits received by the plaintiff from other sources. See Redding v Lee (1983) 151 CLR 117.
Under the common law, very few benefits are deducted from damages awards. The exception is sick pay (see Graham v Baker (1961) 106 CLR 340). This exception has been confirmed several times by the High Court. The exception appears to apply when employers are contractually obliged to pay sick pay.
There is legislation concerning how benefits from some collateral sources should be dealt with. At the federal level, the government can recover money paid as pension or benefits to an injured plaintiff who is later awarded damages. This means that any such benefits received are ignored by the court when damages are assessed and the Commonwealth then has to recover the appropriate amount from the plaintiff.
The situation is complicated by the fact that other relevant compensation schemes (such as workers' compensation and no-fault accident legislation) are state-based and funded. In those states which permit a common law claim notwithstanding the existence of compensation schemes, the provisions generally aim at ensuring that a plaintiff does not obtain double benefits.