"In Castle DLC matchmaking, disable a vehicle and then hijack it."
Is there some special criteria to this one that I'm missing? Two times today I EMP'd a vehicle with the plasmas pistol, then hi-jacked it, but neither time gave me the achievement. Once was on a Banshee and the other was on a Ghost. The only thing I can think of is that you have to do it while the vehicle is still completely disabled from the EMP blast. They definitely were when I hit the button, but the animation is long and they were no longer disabled by the time I had completely taken it over.
Also, are these the only 2 vehicles you can do it on? It seems you can't hijack a Wraith or Mantis, it just does the plant bomb scenario.