It's a lose/lose proposition. CO could go the UA route and layoff most of their onshore reservation people and hire armys of cheap offshore agents to get the wait times down, but then you would be trading in skilled US jobs for less skilled/less well trained overseas jobs.

The happy medium of CO having the same number of people that UA contracts out overseas being hired in the US with US pay/benefits would add to the labor costs significantly.

Two different approaches to the same problem, both have their upsides and downsides.