Try holding the key next to the slot and sticking your finger into the slot - see if the ignition comes on! I'm not sure where the microswitch is, but it's not going to be that small or intricate - the key is quite a blunt object.
If the works, see how far you can get the key away from the slot and still get the ignition on.
As someone says, it might be RFID and have a very short range and actually need to be in the slot - we won't know until it's tried.
Agreed on the 1 series - it will be trying to read data from the 1er key and correctly denying the ability to start the car.