I found this article on Times Online - Ruby Wax is now doing management training and here's her take on it...

All good stuff but I disagree that you can build Self-awareness and Social awareness simply by opening up a discussion in a workshop...

This is fine where you have a group of people who are already aware of their behaviours and are willing to change, but they're probably not the ones that are causing the toxic behaviours in the first place!
A bit problem is that often the problem people are not even aware of their bad behaviours or how they effect the people around them.

Feedback, appraisal and 360 Degree Feedback are great tools for starting those discussions; it's often the shock of receiving unexpected feedback that can bring about the biggest change - but as an employer or trainer you need to make sure you can support people through that.  And here's a link to an article by John Adair about leaders being humble and developing self-awareness http://www.track360feedback.com/2008/10/27/self-awareness-for-leaders/