As I understand it, this funding was for the retrofit of catalysts and DPF's to engines that didn't originally have them. It has nothing to do with the current crop of clean diesel engines. According to the Diesel Technology Forum, for every $ spent on the DERA, there was a $13 benefit in reduced health issues.

retmil is correct, this is another form of choosing winners and losers. The only good thing here was the end of funding for fuel cells, they are nothing more than a black hole.