You can try something like this:
ServiceFactory sf = ServiceFactoryLocator.get("motu","motu");
QueryService qs = sf.getQueryService();
ProcessDefinition pdef = qs.getProcessDefinition("MTAProcess");
Activity activity = pdef.getActivity("Transform");
Application application = activity.getApplication();
if(application.getAllAttributes().keySet().contains("messageTransformation:TransformationProperty")) { //MTA
String[] fields = ((String)application.getAttribute("messageTransformation:TransformationProperty")).split("fieldMappings");
for(String field: fields) {
if(field.contains("fieldPath")) {
System.out.println(field.trim().split("fieldPath=")[1].split("\\s+")[0]); //print target of xform
}
}