Yes, but though a shielded cavity is grounded, it isn't grounding the circuit. Electrically, there is definition for and difference between a grounded conductor and grounding conductor. I modded a friend's MIM Tele a few years ago. It had 2 of those. One in the control cavity, one in the neck pickup cavity. It was factory wiring, and the shielding paint was under the finished paint. Kind of strange because I've been told shielding is useless, it's why the big manufacturers don't do it. Behold the paradox.