They generally bolt to the underside of the upper triple clamp. Most have breakaway bolts that allow you to tighten them once and the head breaks off at a certain torque. Just use a small chisle and a hammer and tap what is there in the direction of loosening.
If you cant get the switch off, just cut the wires, bridge the connections and run them into a switch. That way you will at least be able to ride. Most newer bikes have security bolts like was previously mentioned. On my cbr 900, the ignition switch could be unbolted with a t-40 torx. You didnt even need to remove any plastics.