It depends heavily on what your calling in for, for example if you call in for internet issues chances are your going to get outsourced ( and i don't blame them for this a lot of internet calls tend to be PC/router issues). It also depends on where you live, some areas by contract require certain considerations such as hold time, outage response times..those areas are routed domestically to certain areas that are aware of those requirements. There is also some quality control, if it detects you have spoken to a large number of reps over a short period it has a higher priority to be routed domestically as well as it is obvious your problem is not getting solved.
I think the biggest problem with comcast is that the upper management ignores the lack of quality control and accountability for outsourced support that local agents are subject to. Even if every mistake or bad behavior is reported (which it is not simply because you just don't have the time and have to fix it and move on) the difficulty of reporting that behavior to out of country management team and ensuring that they correct it is alot higher than sending msg to an internal manager/sup.