I'm on BBF fares over 50% of the time, which are "B-up" fares. I've never had to call to get the UG (even if it's weeks out). I think your CO status played a part in the problem.

As a ST Elite +, I'm not sure if you're routed to the elite line. I bet the non-elite agents don't often deal with the Y-up scenario, that could have played into your resistance. I'm sure all the agents up in Chisholm know about the Y-ups.

Just goes to show, be nice, be persistent, and if you don't like the answer, hang up and call again!