Normally with a departing business class boarding pass on a *A carrier you have access to any *A business class lounge. That includes the RCC or a Continental club if there is one in Orlando and it includes the MLL in YYZ. It wouldn't include an IFL (International First Class lounge) if there is one.

The other poster was talking about an Air Canada ticket which included a domestic UA flight. Firstly it's all about the *operating* carrier, not the ticket stock, so this was a domestic flight on UA. Domestic US carriers have strange policies for domestic flights, though I was under the impression that if they were part of an international itinerary they still got lounge access.