Jigsaw works good, sawzall'll do in a pinch... if you're lucky you'll be able to back the tabs far enough off to work with your wall, I got was able to get them in in a house with about 1 3/4" plaster (3/4 PLASTERBOARD over 1/2" drywall, over lathe and plaster)
if you can't you could always shoot a couple screws into the toungue and groove, of course you'd have to leave a couple extra ground wires w/ ring crimps on the end
for grounding purposes
as a last resort
hey, how about those "smart boxes" they sell (or used to) in the webstore? those'd probably work well with the toungue and groove...