A lot of new car sales in the UK are from company fleets. Not sure how it is in the US but in the UK it is very common to be given a company car by your employer as a perk, in the same way you might get a dental or health package. It's also one way of getting around certain tax laws. Trouble is, a lot of companies will also pay your fuel and as such have a vested interest in keeping their costs right down and thus choose a diesel. I worked for a company that insisted that all new company cars must be diesel and this caused a lot of complaints from staff, but the company were saving something like £30,000 a year over their small fleet. A no brainer really. Also, most company cars are kept for about 3 years and will hold their value well too, again helping your employer save money. I'd be curious to see the breakdown in company owned and privately owned vehicle sales though if you have it. I'm sure private owners are more likely to buy petrol.
I don't have any more info than what I read in the article but I can tell you that company cars are not a common perk in the U.S. and that, when people do get cars, the IRS has required fairly onerous record keeping.
