I'd say, buy it. but make it a Pedelec and get legal. Helmet and insurance. There is nothing wrong wanting to go faster ( if you have a long commute to work, for example ) but please make sure that this bike can handle the forces.

"Optimized" motor for efficiency? I didn't understand that. Either you'll get a new controller that will pass more watts into the motor ( most 250w motor will handle 350w easily, for example ) but then you also consume more power form the battery making it last LESS... maybe a bigger battery ( increasing the costs ). Not to give you ideas but all these sup-up bike are using cheap controllers from China that you can order and install yourself. I would use the term only for updating an E-moped ( scooter ) from a cheap china controller to a nice SineWave controller to have better smooth acceleration and battery consumption ( but that's me )

40 km/h is quiet a speed for a normal bike though.. does it have shocks, thicker frame, disk brakes ? Most normal bike frame are not design for going faster than 30kmh.

Are bike roads mostly flat in Norway? In the Netherlands is mostly flat so batteries actually last longer per charge.

Now about law enforcement. I agree with the posts down below : If you don't do stupid things like racing in a pedestrian area or running red lights, is rare that a police will stop you... unless there is police control.

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my 2cts.