Just had a chance to hook up the Turbo suction brush (450644) to the CT Sys when I was doing some house cleaning, and since I don't recall anyone mentioning having tried out this combination, thought I'd report the results.
Short answer: it works, though there is noticeably less power to the brush generated by the 106CFM of the CT Sys (which I had outfitted with the 36mm hose) vs. the 137 of the CT26-48. As long as the pile of the carpet was thin, the brush removed all the visible particles, and did not appear to struggle. The trouble came when I transitioned to a carpet with a thicker pile, and several times the brush slowed down considerably and even almost came to a stop if I went against the grain of the pile, so to speak.
So, if I'm feeling too lazy to fetch my CT26 out of the shop when I'm cleaning my own house, I would still use the CT-Sys with the turbo suction brush. But if I were on a jobsite, I would probably only trust it with the CT26.