In response to my own post, here's an update. When the dealer told me that it probably needed a new transmission, the service advisor said that we could first try to drain and refill the fluid. $400+ later, I drove away and heard the same squeal a couple of times. Subsequently (for a week) the squeal is gone! I've done a lot of city driving this week and have also driven a return trip, Toronto to Buffalo, with NO problems! Hopefully changing the fluid (which they told me was quite dirty) has corrected the problem. I also informed the dealer that I was aware of the Warranty extension in the US, but they were 'unaware' of this in Canada.
Thanks again for the help in this forum.