JBoss XTS Transactions is a fully supported component of EAP 5.2.x. Its bits are located in docs/examples/transactions/jbossxts.sar file and the issue is that this file is not signed.
Please, sign content of the jbossxts.sar properly.
In term of the signing sar is meant singing all jars inside of the sar archive. In previous releases there were some java classes not packed in any jar and this should be fixed by TS dev for the next EAP realese.