Even if it's locked, you can still gain a great deal of information by reading what the ECU is up to. The best place to go for MBE stuff is SBD Motorsport, who sell the Adapter to enable you to interface a laptop to the ECU. The software is free to download and is called EasyMap.
The cool thing about the software is that it offers data logging capablities, so you can go for a drive and then examine the data at your leisure.
With the MBE ECU on my car, what determines whether the ECU is locked or not is the software used to access it. The standard EasyMap software gives read-only access, but I have another version which allows updates to be made. I have no idea whether this is the same on the current ECUs, mine is 8 years old and obsolete now.
