I am trying to support a claim that a Fortune 1000 company with the
opportunity to move all or most of its employees to a single building
or central campus should do so.  Please help me generate references
that support this claim.

This question does not have to be broken out to answer all of the
numbered items separately...they are listed below to indicate my line
of thinking and give more specific guidance.  Please provide academic
research, articles, whitepapers, or anecdotal references for the
following topic(s) to address the request above.

Academic research, articles, whitepapers, or anecdotal references:
1) aimed specifically at quantifying productivity gains from
concentrating corporate staff in a single campus instead of spreading
them out over multiple campuses;

2) related to efficiencies gained by facilitating face-to-face work
environtments for co-workers;

3) for efficiency and productivity gains resulting from bringing work
groups together;

4) for the impact on organizational culture of consolidating staff
from multiple locations into few locations (or a single location).

NOTE: I do not want references to telecommunications product and
service providers, or to anyone selling computer networking products,
consulting services, or similar technology to companies with multiple
campuses or sites.  The following link is an example of what I do NOT
want in the answer to this question:
http://www1.avaya.com/enterprise/whitepapers/maximizing-productivity.pdf