Jelly Bean on the Galaxy Nexus - forcing an update?
There are many variations of the Galaxy Nexus. Most likely, your phone is yakjuxw, which gets the updates from Samsung. The other phone is either yakju or takju, which use Google's own updates, which are released quicker.

The versions are interchangeable, if you don't account for international customizations or possible carrier modifications. For example, see my answer here on how to change the yakjuxw firmware to takju Jelly Bean, which can be then officially upgraded to 4.1.1 via OTA.