I just checked my MP balance and sure enough MILES were deducted for the upgrade and not certificates.

After I was told by the CSR at the RCC, by the PremEx CSR over the phone AND the airport agent that the upgrade would be done using the 500 miles certificates, indeed these can only be transferred to a traveling companion so UAL granted the upgrade and deducted miles without my permission.

Needless to say, I'll fight this, but discourage anyone else from trying it!!

I'll post updates as they develop.

Sorry.