With the federal shutdown over, IRS workers are back to work and starting to tackle the backlog. After 16 days of not opening mail, not processing returns, and not answering phone calls, the IRS is expecting it will take some time to get back to "normal" operations. In fact, the IRS issued a statement urging taxpayers with non-urgent matters to wait to call the IRS. I can only imagine what the call traffic will be like after a 16-day shutdown.
Now that the offices are up and running, employees will be staffing the taxpayer assistance centers and taking calls on the taxpayer hotlines. Employees will continue processing refunds for returns filed before the shutdown and begin to process the returns received since the shutdown, including those returns due on Oct 15 for filers who requested an extension. This tax blog has a good summary of just what activities will get back up and running now that the IRS is back to work.