What is the value added to a business such as Siemens Power generation
that can be created by employing an employee with a PhD in
organization management speacilizing in leadership?

The question is impossible to answer in a strict dollar sense.  The
closest you can get is to range estimates and drivers for determining
the value.

1) Lowest value generated:  The value must be at least equal to the
salary paid to the individual being hired.
2) Drivers of value from the individual:  
Existing environment:  Is the organization currently well led or does
it need reorganization or fresh strong leadership?  Greater value from
having existing poor leadership.
Breadth of responsibility:  Will the individual have the ability to
make recommendations which can positively impact significant costs or
revenues? Greater  value will come with greater authority over
revenues providing recommendations are within the individual's field
of expertise and range of competence.
Willingness of the organization to change:  If the organization is not
willing to change or the individual does not have the backup necessary
to impose change then value will be negatively impacted.
Talents of the individual themselves:  How much individual initiative,
charisma and determination does the individual have?


Upper bound:  If the power generation businesses which have employees
of this type are valued higher than Siemens in the stock market the
maximum reasonable value would be the value difference between Siemens
and the companies employing this type of employee.