AT&T refused to unlock the device for use in Canada, insisting only Apple could do so. Apple then tossed the ball back to AT&T, asking the reader to call AT&T again, because only the carrier could authorize the unlock. When he did, the only advice customer support gave him was to "Just jailbreak your phone."
Jailbreaking the phone could potentially allow him to SIM unlock the phone as well, but not if the baseband wasn't compatible.
At any rate, knowing that current Apple CEO Tim Cook has continued the policy followed by his predecessor, the late Steve Jobs, in occasionally responding directly to emails, the reader sent a plea to Cook asking him to intercede.
The reader didn't get a response directly from Cook, but AT&T Partnership Operations informed him it received an email from Cook requesting that it make a "one time exception" and unlock his iPhone.
In addition, he also received a call from Tim Cook's special assistant following up on the unlock.
"Mid day my wife sent me an e-mail at work saying 'Um, Tim Cook’s special assistant just called and she wants to know if AT&T has unlocked your phone yet??? Why does Tim Cook care about your phone?'"
It's an interesting turn of events, but what it really does is emphasize what a pain it is to unlock a device from a network, particularly an iPhone. Still, most of these emails to Cook, as with Jobs, go unanswered, so we'd say he picked a good one to respond to.
You can find the reader's email uploaded to Scribd here.