The decision is here. I have only scanned it, but have these observations:
1. Cromwell J. authored the judgment - his first significant torts judgment since joining the Court.
2. The causation analysis is pithy, and question-begging:
" I agree with the Court of Appeal that the trial judge applied the wrong legal test for causation. When he wrote his reasons in 2004, the trial judge did not have the advantage of this Court’s judgment in Resurfice Corp. v. Hanke, 2007 SCC 7,  1 S.C.R. 333. That decision clarified the law of causation, holding that absent special circumstances, the plaintiff must establish on the balance of probabilities that the injury would not have occurred but for the negligence of the defendant: Hanke, at paras. 21 - 22; Athey v. Leonati,  3 S.C.R. 458, at para. 14.
 In my view, the trial judge did not apply this “but for” test. The appellants' contention that he did cannot be sustained by a careful reading of his reasons as a whole. Failing to apply it is a reversible error.
 The appellants submit in the alternative that this case falls into the class of exceptional situations discussed in Hanke in which the test for causation should be relaxed to the “material contribution” standard. I cannot accept this submission. As Hanke made clear, the sorts of special situations for which the material contribution test is reserved generally have two characteristics. First, it is impossible for the plaintiff to prove that the defendant’s negligence caused the injury under the “but for” test, and second, it is clear that the defendant breached a duty of care owed to the plaintiff and thereby exposed the plaintiff to an unreasonable risk of injury of the type which the plaintiff ultimately suffered: Hanke, at para. 25. This case has neither of these characteristics. It was not impossible to prove causation to the “but for” standard. The appellants’ submissions in effect demonstrate this: their primary position is that they did so and the trial judge found that they had. Moreover, there was no clear breach of a duty: for the reasons I have given, I would hold that neither Pinkerton’s nor the government breached its duty of care towards the murdered workers. It follows that the “but for” standard should have been, but was not applied by the trial judge.