Just to confirm, I have now committed a unit test that proves Marks assertion to be true: https://svn.jboss.org/repos/labs/labs/jbosstm/branches/JBOSSTS_4_15_0_Final/atsintegration/tests/classes/com/arjuna/ats/jta/distributed/SimpleIsolatedServers.java -r 37580
When flowing the transaction you can just use the value obtained from TransactionTimeoutConfiguration::getTimeLeftBeforeTransactionTimeout(boolean) (/1000)