Starting with 5.0 Infinispan's transaction support was enhanced to allow Synchronization-based enlistment in transactions (v.s. XAResource). A main use case for this is Hibernate's second level cache: by using Synchronization the transaction manager doesn't have to write the log on the disk. On the short, better performance!
You can read more about it here. Thanks to Galder Zamarreno, the integration will be released together with HHH-6062.