When were DPF and DEF introduced on RV diesels?

Yes, a little more complicated, as not all engines had DEF, even after 1/1/10. Navistar, for example used high amounts of EGR to (attempt to) meet the new EPA standards.

But, for most 1/1/10 was ENGINE build date (not chassis or coach) from which DEF systems were fit on the vast majority.

Here is a good 1 1/2 minute video on it: http://www.youtube.com/watch?v=uQHvi2Lgnac