Fun fact: There are more versions of the Samsung Galaxy Nexus floating around, software-wise, than you're probably aware of, even when it comes to the GSM version. The basic rule here is that if you have the yakju version of the Galaxy Nexus, it's GSM, and mysid is CDMA/LTE, in the case of the Verizon Galaxy Nexus. But there actually are regional differences as well, so you might see ykjuux in Canada, or there's yakjuxw, or yakjusc. Probably others. Make your head hurt? Mine, too.
And with that has come great debate over whether the various verisons are updated directly from Google, or from Samsung, or from some magical neckbearded update gnome deep in the forest. As I've said on Google+, so long as the updates come in a timely manner and aren't borked (not that they should be), I couldn't care less whose servers they come from.
But if you are worried about that sort of thing, there's a little tool called "GN Official Update Checker" that makes it easy to figure it out. All it does it check the ro.product.name line in your phone's build.prop file and tell you whether it's updated by Google or not updated by Google.
Whether it keeps you up at night is entirely up to you.
Update: Turns out the CDMA/LTE mysid variant (that's the Verizon Galaxy Nexus to you and me) does actually get its updates from Google after all, according to Googler Jean-Baptiste Queru. So that's that. JBQ also says that yakjuxw and other yakju variants signed by Samsung have only "really small region-specific tweaks".