I thought I would just update this thread for the resolution, should anyone else have this happen. There followed some emails from Air Canada in response to the various complaints (primarily the DOT complaint I believe, since a DOT person was cc'd on some). Each time the AC rep made some claim along the lines of "the cheapest flight meeting the same departure and arrival requirement is $3000", and each time I patiently pointed out that on both the AC and Orbitz websites at that very moment, I could buy almost any AC set of flights meeting the criteria in the email for $1000, and sent the relevant information with a cc to the DOT person. (During this period, AC also changed the times for the flights multiple times, but never for more an hour, or I might have had a refund claim under that.) In other words, I just pointed out where they were incorrect and kept reiterating my original complaint.

However, I then received a phone call from AC out of the blue and they refunded my ticket. The refund has hit my credit card, and though it took a while, is showing as cancelled on the AC website.

Of course, I then rebooked the flight with a one-day change for about the same amount. But on the UA website, not Orbitz or AC (though it does appear on AC using their PNR).

Two lessons: Persistence and formal, factual complaints can pay off. Never use Orbitz.