The Scalability Server an Agent reports to can be changed via command line or via a configuration policy, here is explained both options.
Client Automation - 14.x
If you were to change the reporting Scalability Server of a machine you could do so either by running a command line on the agent machine or by changing the parameter 'Common Agent--> Common' in the configuration policy on the domain manager
Important Note: If the Scalability Server the Agent was reporting to is no longer available, then the Configuration Policy method will not work. You will have to use the command line method (using a script/login script) to re-direct the agents to a new Scalability Server.