The locked ECUs can only be unlocked by MMC and they won't do that as they are set to meet emissions regulations. Those who had their car supplied with an unlocked ECU were just lucky.
Also if purchasing a new unlocked ECU check it is physically compatible with your car. The wiring loom and connectors are different for EU3 and EU4/IVA cars and I have also heard that there was another change in design earlier this year.
