well it is not quite sure beeing about the IMEI, but multiple rumors think its IMEI based!
Well I guess it doesn't matter actually ...
Unfotunately the Motorola Software Update (the program used to update SW on Moto phones) is not supporting Android phones as it seems, so there is no way of bringing a firmware there. Anyway if per chance somebody succeeds using Motorola Software Update and it flashes an updated firmware, don't hestitate to upload it (because root).
I used phones which had different operative systems developed by Motorola, and those were updated with MSU. But Android is an OS developed by Google. Motorola works on it to adapt it to its own hardware, but they don't change it that much in order to add a custom software updater.
If there is any "official" way of updating Android OS using a software (by google?) in the computer, Motorola might be able to add a capability to MSU to make the phone think it is Google's software.
But I understand that to update the phone manually, you have to put the update file on the SD card and then restart the phone in a special way and it updates. Actually, I'm not sure if this is only for rooting the phone.
Rodrigo.