com.arjuna.ats.internal.jta.transaction.jts.BaseTransaction has the following:

try
{
return theTransaction.getStatus();
}
catch (NullPointerException ex)
{
return javax.transaction.Status.STATUS_NO_TRANSACTION;
}

This mean's that anyone trying to debug a NPE with an exception breakpoint will constantly hit this, as well as being much slower than a simple null check.