What is the test for dismissing a co-defendant on a Rule 18A application?

In Insurance Corporation of British Columbia v. Hilbar Enterprises et al. 2005 BCSC 974, Ralph J. relied on the reasoning in Thompson and refused to dismiss a co-defendant on a Rule 18A application because there was an inadequate evidentiary basis to confirm that the remaining defendants would not attempt to throw the blame on the absent defendant to the detriment of the plaintiff and this was particularly so where in the statement of defence one of the remaining defendants alleged that the accident occurred because of the negligence of the defendant seeking relief under 18A.