This doesn't seem to be done ATM, as these hashMaps are built in the LocalTransaction objects and are plain HashMaps.
I guess this won't bite use till we'll use transactions over hotrod, as at that point the keys will be byte arrays. Still would be nice to build all our key manipulating collections through the CollectionFactory, i.e. all the collections that hold keys in LocalTransaction and RemoteTransaction (plus base classes) + InvocationContext implementations.