Some agencies have a budget for the full year and are not affected by the shutdown. These include the departments of Defense, Health and Human Services, Education, and Labor (includes the BLS). Some agencies are not funded by Congressional appropriations and are also not affected (Fed Board, FDIC, CFPB, and some of the other financial regulatory agencies).
Agencies that are affected by the shutdown are the Departments of Transportation, Housing and Urban Development, State, Interior, Agriculture, Treasury, Commerce (includes Census and BEA), Homeland Security and Justice. Plus some independent agencies (the FTC is the only one I can think of in this group that hires economists). These agencies will not be able to interview during a shutdown. The key day for the shutdown to be resolved is next Wed. That will be the first workday of the shutdown (Monday and Tuesday are holidays). On the first day of the shutdown, you go to work for 4 hours to do shutdown related work (set an auto response on your email, put stuff away, and turn stuff off). Affected agencies that are planning to interview in Atlanta should use this time to contact the candidates to let them know what the plan is. After Wed morning, the agencies go into shutdown mode and won't be able to contact the job candidates or reply to emails until they reopen. It is also likely that they will have to use these 4 hours to cancel all upcoming trips, so even if the shutdown is resolved on 12/31 they might not be able to rebook everything in order to interview in Atlanta. In the case that the shutdown is resolved between now and the meetings, they'll be able to let you know what their plans are once the government reopens.