I have noticed ARB (Air Rescource Board) now has their own pickups and mobile inspections. They will pair up with the regular DOT inspectors at roadside inspection stops. Some of these are in the normal areas for portables, but they are also targeting high truck traffic locations, like right outside the quarries. Recently in Irwindale I spotted 7 DOT, and 4 ARB trucks set up at 4 locations, catching every possible way in or out of the area in a truck.
Also, pay attention to the ENGINE year, not the truck year. most 2007 and lots of 2008 trucks have 2006 engines, as the manufacturers were not up to speed by the time the deadline hit for the new engines. You may buy a 2007 or 2008 truck only to find it is still not legal.
The other thing to think of is the troubles with the first few years of these engines. Many of them are just not reliable, and are prone to leave you walking.
It is a shame that the government has done this to the little guys. The big companies willingly go along, as it reduces their competition.