On one occasion when an application was made before the Canadian Human Rights Tribunal to permit one of the witnesses to give evidence, our lawyer had to state the case as to why a great exception would be made to the usual. The foundation of that was based on concerns of potential security or safety. But it's up to the tribunal then whether or not to accede to a request. That was made in one instance, and I'm only aware of one instance.
On June 16th, 2009. See this statement in context.