What I would do, is get a rip that supports this printer in CMYK mode (EFI eXpress, Fiery XF, Colorproof XF, ...), and create a profile using i1Profiler's 'Full Black Separation'.
A strange and expensive approach as the HP driver itself excludes any composite greys in the B&W mode and does almost the same in color mode when fed with neutral RGB images. A fresh calibrated Z3100 (with its integrated spectrometer) already lays down a linear B&W tone range in B&W mode with a very high Dmax on matte papers. The Z3200 is usually less linear and may sacrifice some density in Dmax when the print is linearised through a QTR B&W profile workflow. At least in what I experienced with the two Z's I have. The B&W mode in general delivering a better Dmax than the color mode if used for B&W prints. I do not see iPublisher improve on that. A better color print may be possible with the Eye One Pro 2 and iPublisher profiles but that is not what the thread is about. The RGB-device profiled HP driver does a good job for this N-color printer, a RIP with skilled color management people using it may be able to beat that but I have seen more tears shed from people buying RIPs than from people not having them.
Met vriendelijke groet, Ernst
360+ paper white spectral plots:http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
september 2012: Photokina updates going on for at least a month