it is possible to add jmx hook to obtain Hibernate Search SearchFactory Statistics by using this property :
<indexing enabled="true" indexLocalOnly="true">
<properties>
<property name="hibernate.search.jmx_enabled" value="true" />
</properties>
</indexing>

tough this property does not allow multiple registration (one registration per cache).
it would be nice to wrap the Statistics object from HibernateSearch into the actual cache object mbean.

i guess the implementation could look like this :
// get search factory statistics
org.hibernate.search.stat.Statistics statistics = Search.getSearchManager(org.infinispan.Cache).getSearchFactory().getStatistics();
// wrap search factory statistics
SearchFactoryStatisticMBean mbean = new SearchFactoryStatisticMBeanImpl(statistics);
// expose mbean
ManagementFactory.getPlatformMBeanServer().registerMBean(new ObjectName("..."), mbean);