I'm rather ignorant to the backend details, but since the merger I did some reasonable amount of flying on CO this year. I've made a couple observations that do support Channa's points:
1) Any issue with a CO agent seems to require inordinately large amounts of typing and time relative to equivalent UA agents. I'll presume that the two sets of agents are equally competent when drawing conclusions.
2) Several times I've had agents tell me things about upgrades or standbys that just weren't true. For example, they've claimed to add me to an upgrade list and then the next agent says that I'm not on it. Either the first agent never did it or the system screwed it up.
3) The upgrade system is incredibly confusing/opaque. Even when EUA is working correctly, it's still a bit baffling. With the sweeps it's impossible to tell the difference as R can be >0 but no one is upgraded until the next sweep.

This IBM mainframe thing is scary. I had no idea what an old-fashioned system they were using. They must spend fortunes custom-building everything. Lots of businesses have learned the hard lesson of getting stuck with legacy systems that end up impossible to maintain. Sometimes the problem is that no employees under 60 know to program them at all.