Having enabled setting I've verified the traffic in omniture is being recorded against the google proxy (US), At present the setting doesn't appear to be enabled by default, and therefore not much impact.
Towards the bottom of the article referenced ..
As a site owner, how do I perform IP geo-targeting? The IP address of the mobile device is forwarded to the destination server via the X-Forwarded-For header. Site owners should check for this header to correctly determine the location of the user based on client's IP address.
Are Omniture aware of this and is something being put in place ?