The UCX release 7 software has that capability. If you look at the drop down box on the Software Update page, the last source listed is "Local (USB)". This option is intended for hardware devices that don't have access to online repositories for some reason (security, no Internet connection, etc.). You should contact E-MetroTel about how to the USB stick with their software updates.
Unless you have many UCX systems without Internet access, a simpler option might be to use your laptop with Internet connection sharing as a temporary Internet access device to run the update of the UCX system.