Re: While no other manufacturer was using a similar system to Volkswagen's ...
Though to be pedantic, others have been caught doing the same thing in different ways - such as using the GPS to determine if they are in a test facility !
The thing that needs to be remembered though is that these cars passed the legally mandated tests<period>. I would argue that they didn't actually break any laws, because I doubt they actually claimed anything other than having passed the tests (and using the official consumption figures that also come out from the tests).
The law (AIUI) is clear - the cars have to be put through a specific cycle under specific conditions, and under those tightly specified conditions, they have to meet certain limits.
So this is very much like all those "international company isn't paying enough tax" complaints - just that, a complaint but without foundation. If the results are wrong, then look at the process that leads to them - don't complain about people complying with the laws as written down.
This is different to (say) someone putting legal tyres on a car before it's MOT and then putting bald ones back on afterwards. There is nothing wrong with this in terms of the MoT test - but there is a law against driving with bald tyres. In this case, there isn't actually a law against emitting much more on the road than in the tests.
But this is just yet another example of unintended consequences. You define the tests, people will work to passing those tests. I fail to see what's so hard to understand about this.