What is the test for delivering an expert's statement at trial?

The trial judge pronounced his reasons at the opening of the tenth day of trial. He began by referring to Tsoukas v. Segura, 2001 BCCA 664, 96 B.C.L.R. (3d) 344, a case involving what was then Rule 40A [Evidence of Experts] of the Rules of Court which provided, in part: (2) A written statement setting out the opinion of an expert is admissible at trial, without proof of the expert's signature, if a copy of the statement is furnished to every party of record at least 60 days before the statement is tendered in evidence. (3) An expert may give oral opinion evidence if a written statement of the opinion has been delivered to every party of record at least 60 days before the expert testifies. . . . (15) At trial, the court may dispense with the requirement of delivery of a statement. (16) Without limiting the generality of subrule (15), the court may dispense with the requirement of delivery of a statement on one or more of the following grounds: (a) where facts have come to the knowledge of the party tendering the witness after the delivery of the statement of that witness’s evidence, that could not, with due diligence, have been learned in time to be reduced to a further statement and delivered within the time required by this rule; (b) where the non-delivery is unlikely to cause prejudice (i) by reason of an inability to prepare for cross-examination, or (ii) by depriving the party against whom the evidence is tendered of a reasonable opportunity to present evidence in response; (c) where the interests of justice require it. (17) Before or at trial, the court may extend or abridge the time limits set out in this rule.