Update 2: Verizon has confirmed that it is in fact an update to Android 4.1.2, not Android 4.2, as the screenshot below now reflects.
Update: It sounds like this may be an Android 4.1.2 update, not Android 4.2. The build number JZO54M is, according to Google's own codename site, an Android 4.1.2 build (specifically, Android 4.1.2 R2.1). Sounds like Verizon done goofed. We've reached out for confirmation, but I'd be skeptical if the Verizon XOOM suddenly bunny-hopped from Android 4.0 to Android 4.2.