"Graham Harrison" writes:
(snip)
Something doesn't feel right in my explanation but based on what I see on
the Toronto Pearson airport website
http://www.torontopearson.com/Connecting.aspx that seems to be the process.

Yes -- admittedly, I don't recall what happened with customs, but I
think I had a Halifax - Boston flight that had me do the US immigration
bit in Halifax on the way out, which was a surprise.

-- Mark