A Mobile Command Unit was a base of CTU operations away from the main building. They could be set up to manage certain crises while also being close enough for field agents to monitor the situation.
A Mobile Command Unit was set up outside the United Nations building at around 11:10pm (four hours prior to the signing ceremony) to help security protect the signing of the peace treaty which was due to occur at 3:30pm. Specifically, the Mobile HQ was set up on the first floor adjacent to the High Commissioner's Office. Once it was set up, all available field units were sent there.
The command unit consisted of a large metal building with many computers inside for analysts to work at. There was also a space outside designated for field agents to arrive and leave as necessary. Included with security at the command unit were SWAT vans and dogs.