Sharing my steps, let me know if I need to do something differently:
I'm already using the last successful nightly AS8 (build version 1498) from https://ci.jboss.org/jenkins/job/JBoss-AS-7.x-latest/ so I didn't change.
I go to jboss-as-8.0.0.Alpha1-SNAPSHOT/modules/system/layers/base/org/jboss/ironjacamar/impl/main
and move ironjacamar-core-impl-1.0.15.Final.jar* to a temp directory.
I copy in the new version, ironjacamar-core-impl-1.0.16-20130314.184732-1.jar
and I update module.xml to replace the reference of ironjacamar-core-impl-1.0.15.Final.jar to ironjacamar-core-impl-1.0.16-20130314.184732-1.jar
Attached is the server.log from my test run. This run did have the previous byteman script enabled. Searching the log for ERROR, I still see the " Attempt to start a transaction while in an active (global or local) transaction" issue but I also see a new error message that precedes it,
13:00:56,127 ERROR [org.jboss.msc.service] (MSC service thread 1-4) MSC000002: Invocation of listener "org.jboss.as.connector.util.RaServicesFactory$1@3745dc3b" failed: java.lang.IllegalStateException: JBAS014666: Duplicate resource resource-adapters