I even asked the troopers (off-line, during a break) at my CHL Instructor's class about holstered in the car under MPA. It's not a stupid question, and it comes up all the time. The party line answer was that holstered in the car, as long as it's concealed, meets the definitions of MPA.
--BUT-- (you knew there was a but, didn't you?)
The plain and simple answer to "what if I'm asked to step out of the car by an LEO" was that there have been no test cases, so there's not a good answer for the LEO on the street (which of course is different than in the courtroom.) In short, it would depend upon the individual officer. One of the gentlemen I was talking to suggested he would likely have no problem with it, but the other one I was talking to suggested he might, depending on the "totality of the circumstances" -- and both of them are generally pro-carry. They'd like to have a straight answer to the question themselves, BTW.
Unfortunately, with no test cases, nobody can give a "straight" answer to this one. By the letter of the law (MPA) holstered in the car, concealed, is just fine. The rub comes into play if asked to step out of the car. I would think that one could make a good case that, when acting under the direction of a police officer, you couldn't be held responsible for UCW (unlawful concealed weapon) since there was no element of intent or recklessness. PROVIDED YOU CAN AFFORD TO MAKE THE DEFENSE (the usual rub in such cases, especially where there's no precedent).
I am not a lawyer, and I didn't stat at a Holiday Inn Express last night.