Passengers do experience significant problems, given that they're getting refunds from Air Canada directly. For example, when passengers used their vouchers to try to get a ticket, and the second ticket was cheaper, we have reports that passengers are being told that they are only going to refund their cheaper ticket but not the difference between the two tickets.
In terms of third party providers, there are significant concerns. Expedia.... FlightHub is a particularly bad offender as far as we can see so far. In some cases, travel agents are asking passengers to pay an extra fee for getting their refunds, even though travel agents can keep their commission from the airline.
The solution and the answer to this would be—and is—that ultimately it is Air Canada's responsibility and the airline's responsibility to refund the money the airline has. They cannot pass the buck to the various travel agents. This is another significant flaw in the deal and something Air Canada has been pushing very hard for, but legally we have doubts about its validity. We are aware of a prior court decision that confirms that regardless of which intermediary is involved, the airline still has the same responsibilities.