I never could figure that out except to think it must be some sort of EMI that the banks security systems was leaking/interfering with something in the ECU or such in the car.
In another life I was a sound engineer for a television network and had to deal with EMI and RFI all the time when running wireless mics etc..and your suggestion of EMI interference is a very real phenomenon that exists, not sure if applies to this however. You reminded me of a road trip I took many years ago, driving a '94 Volvo 850. I returned to the car with the entire family and the doors wouldn't open with the key fob. Odd I thought. Why the sudden failure? Then I looked up and realized we were parked directly outside the doors of a television station with a huge transmission tower on the roof. I just smiled and drove away pretty much knowing what had just happened. I drove away and the problem never returned....