Is it common for the government prosecutor to concede with the accused on filing a 5K2.11 motion?

If what you are referring to is a downward departure from the guidelines based upon US Sentencing Guideline Section 5K2.11 under a "lesser harms" theory, it is not common for the prosecutor to concede this point in federal court. Sometimes, a prosecutor will state no position on this type of motion. To be safe, the defense lawyer should negotiate with the prosecutor on this issue, and the government and defense positions should be stated in the plea agreement.