You're right, relay interpreting is something we try to avoid when possible, but there are circumstances where it's required. If we had an indigenous language, typically, most of the interpreting of an indigenous language would be done to and from English, because the majority of Canadians are English speakers. It also depends on the contact between the languages. In Quebec, there would be more indigenous languages interpreted to and from French. We try to avoid it when possible.
A good example of this is the G8, which we're currently servicing right now. Where possible, we try to have interpreters who can do French to Japanese and German to Italian, but we can't cover all language combinations, so we do our best.