I've found a way to catch the update without an activated phone: accept the moto terms by first going into system update, then connect to a wifi network and wait a while (for it connect w moto update servers to tell them you need the update). Then put the phone in airplane mode. This will trigger an update is ready notification--hit install. now connect to your wireless network again and it should start downloading. when it finishes, it wont ask to install. instead restart your phone, and put it back into airplane mode. the update will ask to install, hit okay and it will install!
here's the Blur_Version.2.3.20.A955.Verizon.en.US.zip that i pulled straight from the /cache folder where the update was downloaded.
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Hope this helps! :)