From the Kodak website FAQ on BW400CN:
[QUOTE
Can I print BW400CN Film on black-and-white papers?
For optimum performance, print BW400CN Film on professional color negative papers such as KODAK PROFESSIONAL PORTRA ENDURA or SUPRA ENDURA Papers.
BW400CN Film can be printed on traditional black-and-white papers, but the printing time will be substantially longer and require a higher contrast grade of paper (3 1/2 to 4).
For best results printing onto black-and-white papers, we recommend use of a traditional black-and-white film such as KODAK PROFESSIONAL TRI-X or T-MAX Film.
/QUOTE]
It's essentially a color film (in structure and sensitometry). It has enhanced green sensitivity. It has a straight-line curve that extends over 10 stops with a fairly usual Dmax. The design aim was to have a quality black and white film that could be processed along with C-41 color films on the same lines, for both development and printing. This is different from Ilford XP-2+ which, while it can be developed in normal C-41 lines, seems to be designed for ordinary black and white printing.