I have worked for a fortune 50 company and one of the largest pharma companies in the world, and am well aware of how large corporations work. And they don't get off with a: "the worker bee did it" with me.
Let me share a probable scenario with you:
The background: VW is not selling diesels in North America because their emissions don't meet EPA standards. If they put the additional Mercedes catalyst on it, they lose fuel economy, making them just another competitor with no edge in small to upper mid sized cars. The board is being pushed by stockholders to regain diesel market share in NA.
The initial construction of the crime: The CEO tells the upper managers that they must get back into that market. So they tell the middle managers and they have their engineering and tech teams integrate the Mercedes catalytic NOx reduction system, but it adds weight and reduces fuel efficiency.
The sales folks tell the CEO that they have to have the fuel efficiency or it won't sell. The CEO shares the news with the board who says, and THIS IS THE CRIME (ON SOOOO MANY LEVELS, eh?! eh?!! so pay attention!) The word sent back down is: "Well it has to achieve the fuel efficiency and the emissions limits." Knowing that it can't be done in the time given, nor for the resources provided, ...unless. Well one of the managers knows that they had to install a bit of software code to run the car on the dyno and override the traction control and other safety features that would ONLY be done when it's being tested under load. That's what a dynamometer is a calibrated, measured load. And he also knows that the only way the vehicle can get the higher mileage is to turn the NOx limiting EGR controls off. When the EGR (introduces already burned, but cooled exhaust back in to reduce the combustion temp) system is turned off the fuel economy of a diesel increases as much as 15%.
Somewhere a Manager of that company was aware that this was the only way to achieve both objectives. Whether it was filtered to the dearly departed last CEO asshole with the golden parachute (hopefully So He Thinks! Only!) or whether he got the cold hard facts, unfiltered by the multiple politicking Grima Wormtongue's in the middle makes NO DIFFERENCE TO ME. And it shouldn't to you, assuming you are also a homo-sapiens with specific biological requirements including clean air and water. He and the board all need to be sent to prison (etc. etc) as the *CORPOREAL *representatives of the corporation, for the fraud.
As long as we agree to all the above, I'll agree that the engineer did it!