Are you pointing about the Transaction manager service that is part of the application server.
You can look up the the transaction manager service that is available in application server ( below code for Jboss 4.0.).
While setting the environment
//Set the environment details
Environment env = KnowledgeBaseFactory.newEnvironment();
env.set( EnvironmentName.ENTITY_MANAGER_FACTORY, emf );
env.set( EnvironmentName.TRANSACTION_MANAGER, getTransactionManager());
env.set( EnvironmentName.GLOBALS, new MapGlobalResolver() );
I am looking up the transaction manager and using it
InitialContext ic = new InitialContext();
TransactionManager tm = (TransactionManager) ic.lookup("java:jboss/TransactionManager");
Hope it helps .