EV mode speed limit of US vs European models

The common knowledge is that the EV mode is limited to 34 mph. However, on my 2004 European Prius, this is not true: The limit is instead only 27 mph. (The real speed, the one available on the CAN bus. The dash shows the equivialent of 31 mph.)

27 mph corresponds to exactly 50 km/h on the speedometer. 50 km/h is the speed limit of most typical Swedish cities. I don't think this is a coincidence. 34 mph was probably selected since it matches the 35 mph limit, which as I understand it is fairly common in the US.

So now that we know that the speed differs between regions, one obvious question is which device that contains this setting. I guess it is the Hybrid ECU? In that case, I wonder if it would be possible to install a US ECU in a European car. Or learn how this setting is programmed...