No, you're on the right track.
With WMI you should be able to query those blades.
Most of the time there are some prerequisites that need to be fulfilled before it works.
Unfortunately I don't have any IBM Blades to try it out right now.
Yes, that book link was invalid, seems that the website was abandoned.
I replaced the link in the footer, but there is also a link on my blog.
Blog: lucd.info Twitter: @LucD22 Co-author PowerCLI Reference