Just a heads up.
Several months ago, I changed the ceiling fluorescent fixture in the room where I do my electronic work. For the first time since then, I fired up my scope. When I attached the probe, I noticed an unusual 40KHz signal when the probe was not connected to anything. By moving the probe around, I found the signal was coming from the fluorescent fixture. Then, I remembered - this fixture has a new "electronic ballast" using the same principles as CFLs.
So, if you run into such a strange signal after changing a light fixture, be prepared aware. A meter from the fixture, the signal is small enough to barely detectable. When the probe is connected to something or the ground lead is connected to the probe nose, it is gone.
Again, just a heads up. I'll bet this will become more common as these fixtures are installed more and more.