If you have created a WTX transformation map and would like to call it as part of your message flow you will have to install Webphere Transformation Extender for Integration Server.
http://publib.boulder.ibm.com/infocenter/wtxdoc/v8r3m0/index.jsp
It provides installation and integration support when combining WebSphere Transformation Extender with additional IBM products. It includesWebSphere Transformation Extender components that are ready to deploy in message and mediation flows. WebSphere Transformation Extender complements the native capabilities of these products, and can process large documents and messages with more complex formats that are not based on XML.
Thys Michels Blog 
Hi Thys
Do WTX Map nodes report statistics in Tivoli for Messaging and WMB?