Here is the official FAA flight restriction for Fort Calhoun:

http://tfr.faa.gov/save_pages/detail_1_6523.html

It only covers a fairly small area, and has been in place since June 6. Any new restrictions should appear here:

http://tfr.faa.gov/tfr2/list.html

The restrictions aren't wide enough to make photography of the site impossible, so it doesn't look like they're covering anything up, yet anyway.