The rationale for the tribunal is that an administrative means of addressing the claims is probably more efficient and more equitable than the court system in dealing with a large number of claims. So the criteria are provided in 31(1), where they say that the Governor in Council believes it's in the public interest to establish a claim, having regard to the extent and the estimated cost of the damage--so a large incident--and the advantages of having the claims dealt with by an administrative tribunal.
On December 2nd, 2009. See this statement in context.