This is the sort of finding that may not lead to any change to what's already been done, and can easily lead to changes in the future. If it turns out, as indicated in the article, routine operation of vehicles are in conditions which result in the NOx controls being turned off, even if that's a behavior that is currently allowed in the regulations, it's not hard to imagine those regulations and associated testing being updated. An obvious update would be to establish what the permissible level of NOx emissions would be when ambient temp is below 10C.
I'd be willing to bet that no government is going to go with a 40x threshold when the temp goes under 10C.
More simplistically, you can meet the letter of the law while violating the spirit. Some of the reaction you're seeing here are people that see this as violating the spirit of the law, even if it meets the letter. I happen to agree with that stance. Being legal doesn't mean you're being moral, and 40x NOx levels under moderately cool temperatures isn't moral (though it may be necessary for the technology to perform), at least IMHO.