The New Jersey Supreme Court, in a landmark decision that was a year in the making, has taken a big step toward dismantling the exclusivity doctrine of the Workers’ Compensation Act, which immunizes employers from tort liability. The 3-2 decision last Wednesday came in the case of a laborer for a nonunion shop who died when he was run over by a dump truck driven by a worker from a union shop owned by the same principals. The justices said the laborer’s widow can sue the shop that loaned the truck driver even though he is immunized from suit.