811 Peachtree by
jwbab, on Flickr
The fencing at 811 Peachtree Street (EVIVA) covers only the area above in red, with an open gate marked in orange. They just freshly repainted the parking spaces and the lot looks cleaner than usual. As someone else suggested, It looks like they are simply trying to prevent people from driving over the ledge along Peachtree Street or obstructing the sidewalk on 6th Street, both of which are common occurrences.
Technically, Midtown's zoning prohibits the installation of chain link fencing in sight of any public right of way. So, unless this is construction related, they shouldn't have put up the fence. This is why I suggested earlier that it may be related to construction parking/staging for either the Hanover Midtown or Juniper @ 5th project, which are both nearby.