Depending on the UCM version there may be more or fewer direct requests to facilitate this, but you should be able to get it done.  Lookin at UCM7:
 - A 'process node' is a UCM node in the cluster
- The special process node with name 'EnterpriseWideData' is a placeholder for the enterprise parameters
- You can either get a dump of the processnode table (via <executeSQLQuery> like 'select * from processnode') or use <listProcessNodeByService> if you know the Service you're looking for (probably won't get the EnterpriseWideData node that way), to get a list of the UCM nodes in the cluster
- You can use <listServiceParameters> to get a list of parameters on a node, the following gets all enterprise parameters: 
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ns="http://www.cisco.com/AXL/API/7.0">   <soapenv:Header/>
   <soapenv:Body>
      <ns:listServiceParameters sequence="1">
         <nodeName>*</nodeName>
         <serviceType>Enterprise Wide</serviceType>
      </ns:listServiceParameters>
   </soapenv:Body>
</soapenv:Envelope> 
- <getServiceParameter> is used to retrieve a particular parameter, e.g.: 
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ns="http://www.cisco.com/AXL/API/7.0">   <soapenv:Header/>
   <soapenv:Body>
      <ns:getServiceParameter sequence="1">
         <name>ClusterSecurityMode</name>
         <processNodeName>EnterpriseWideData</processNodeName>
         <service>Enterprise Wide</service>
      </ns:getServiceParameter>
   </soapenv:Body>
</soapenv:Envelope> 
Note, you can also change service parameters via <updateServiceParameter>.  You can deal with service parameters more directly via SQL, the main tables involved: processnode, processconfig