It's not implemented as nobody asked for that. Under partition, the safest thing to do with invalidation cache is to wipe it out, ignore any write operations and return nulls for all reads. If the partition handling worked as in dist/repl mode, writes would throw an exception (and some reads too) - I am not sure if Hibernate would handle such behaviour well, it would probably just fail all operations.
Nevertheless, it seems that it could be an useful feature. Please, fill a JIRA for partition handling support on invalidation caches.