Is there a way to soft proof black and white images when using the ABW mode?
Yes, but there isn’t a built-in way to do it. You need a spectrophotometer such as an Eye-One Pro to build a grayscale profile or a set of output curves. See here for details. If you don’t have a spectrophotometer, you can still get very close screen-to-print matches for neutral black and white images as long as you follow the steps listed here.