In a way you have replicated part of the studies done by Mayo, Roethlisberger and Dickson first reported in Rothlisberger and Dickson, "Management and the Worker," 1939.
Unless your control group was isolated from both formal and informal communication networks, you were bound to get a "Hawthorne effect." The hypothesis is that increases in worker productivity were not related to change but to the fact that they were being observed.
The structural changes you describe seem imposed upon the culture rather than a cultural alteration. The underlying culture is probably unaltered and will revert to more comfortable norms when the experiment is over.