I have just installed bbPress and this plugin.
I activated the plugin and in the bbPress widget, I placed bbPress search widget.
When I go to the forums page, the bbPress-specific sidebar doesn't seem to appear - at least I don't see the bbPress search widget. Also, the CMS/normal sidebar doesn't seem to be removed - the sidebar seems exactly like the sidebar for the rest of the site.
Finally, I tried selecting single.php as default forum wrapper. But this doesn't seem to make any difference at all - I still see the *normal* 3-column/2-sidebar page when I visit forums.