If this is a major issue - you can always put your CA key inside one of those Anti-Static bags that they deliver integrated circuits in (eg computer memory cards).
The metal film in the bag forms a Farraday Cage and stops the signal from the key being read by the car.
I keep one handy for putting toll tags in when I carry them in my car, so that I dont get charged a toll from more than one of the tags at the same time.
(and to stop anyone from asking - I have to carry a spare tag for any loan car I use when I am getting my car serviced / repaired as my regular tag was conveniently glued permanently to my windshield by the dealer on delivery - real clever
.)