I haven't measured CPU usage yet in great detail but my framerate is the same with and without. About 48FPS with the 10,000 static obstacles after I did away with the deprecated behaviors I was using early on and forgot to get rid of until now. My computer is fairly powerful, especially for its time, but its "Achilles' heel" is the video card, being a 5 year old mid ranged at the time piece of hardware which I thought maybe that was the reason I can't handle as much as some other people probably could running the same C2 games. My webGL works just fine, the renderer value in my C2 game says webGL and I tried a webGL test you posted a while back on the forums and nothing was blacklisted.
What surprised me a little was how expensive solid behavior really is. So I did a solid type of behavior code from scratch and it works even better.