Use task-status operation to learn the status of a specified task.

Request 

<packet>
  <extension>
    <call>
      <plesk-multi-server>
        <task-status>
          <id>9</id>
        </task-status>
      </plesk-multi-server>
    </call>
  </extension>
</packet>

Response 

<packet>
  <extension>
    <call>
      <result>
        <status>ok</status>
        <plesk-multi-server>
          <task-status>
            <status>done</status>
            <status-message/>
          </task-status>
        </plesk-multi-server>
      </result>
    </call>
  </extension>
</packet>