CopyItem and MoveItem operations in Exchange Web Services can return the Item ID after you install Update Rollup 4 for Exchange Server 2007 Service Pack 1

<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" 
               xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
               xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <soap:Header>
    <t:ServerVersionInfo MajorVersion="8" MinorVersion="0" MajorBuildNumber="595" MinorBuildNumber="0" 
                         xmlns:t="http://schemas.microsoft.com/exchange/services/2006/types" />
  </soap:Header>
  <soap:Body>
    <CopyItemResponse xmlns:m="http://schemas.microsoft.com/exchange/services/2006/messages" 
                      xmlns:t="http://schemas.microsoft.com/exchange/services/2006/types" 
                      xmlns="http://schemas.microsoft.com/exchange/services/2006/messages">
      <m:ResponseMessages>
        <m:CopyItemResponseMessage ResponseClass="Success">
          <m:ResponseCode>NoError</m:ResponseCode>
          <m:Items>
              <t:Item>
                <t:ItemId Id="..." ChangeKey="..." />
              </t:Item>
          </m:Items>
        </m:CopyItemResponseMessage>
      </m:ResponseMessages>
    </CopyItemResponse>
  </soap:Body>
</soap:Envelope>