I looked around, on the official site, and other sites, and there is no mention of the birate for the 1180. Since there's "secrecy" regarding that info, I assume that the 1180 is not 24bit. If it was, they'd tout it like it was gold.
Recording on the BR1180 is 16 bit. Internal AD and DA conversion as well as signal processing (ie the mixer) are 24 bit. I easily found all the specs on this machine before purchasing it... Online.