Looks like a totally standard reply letter. They just cut and paste the relevent bit in about how much you need to upgrade.

A chap I know (really it might have been Thai and not Cathay) just found himself chatting at the check-in to the airline rep. He was checking in with his C class ticket and had gold with EVA. Said he'd happily consider switching more of his flights to Cathay but having gold with EVA and not with Cathay was a barrier to changing. She made a phone call and a couple of weeks later a gold Cathay card turned up.

Seems to me you need the personal touch, luck in terms of access to someone who can make a difference, and a bit of credibility. He was there with his C class ticket and his story made sense. Knowing him, I doubt whether he was at all pushy.

Unless there is an absolute policy against such things, I reckon its possible.