The IT locations of Austin, Chandler, Detroit, Roswell, and Warren were chosen so that GM could get the best and brightest IT talent in these locations. It would always be required when insourcing IT because there are only so many high level technology professionals willing to tough out Detroit winters.
Outsourcing would be a complete failure as the time difference, and quality difference American born and bred engineers give you makes all the difference. Anybody that has outsourced IT know what problems occur with it. They overpromise and underdeliver. When you need a new feature in a GPS system that has to run perfectly to maintain confidence in the American public you have to employ the best, and GM IT is the best in business.