NHibernateUtil.Initialize can't be used for Evners collection proxies. For non-collection proxies however it already works ok.
It would be nice, if we could use NHibernateUtil.IsInitialized as well as NHibernateUtil.Initialize for Envers collection proxies too.
The CreateToOneProxy in DefaultEnversProxyFactory already produces a proxy which can be used by NHibernateUtil.Initialize to Force-Initialize the collection. The CreateCollectionProxy should return an implementation of IPersistentCollection, which it doesn't do yet.