I say it wont work because the checksum will fail.The ESN wont match the other radio and it will tank.Hey ya never know though.
I agree, if the ESN is being checked in say a paid upgrade. I think it would prevent people from upgrading more than one radio with the same payment.
At present, I am not aware of the Firmware or DB updates being specific to each scanner but to a scanner type, like a 436 update only for a 436. However, as you say we are guessing and since details are always important and I do not have them, I definitely could be wrong.
Now I am even more interested to know if it will work or not.