From what I read on the internets, WCF Data Services seem to be bound to data access via Entity Framework on the server.
Is there a way to have NHibernate access mapped in the same way?
WCF RIA Services can certainly be used with NHibernate, and I believe WCF Data Services can too. Both frameworks build on top of IQueryable<T> which can be provided by LINQ to NHibernate
See this post from Brad Abrams, where he uses RIA Services with NHibernate.
WCF Data Services and NHibernate have limitations you should be aware of. There is a bit more to the picture besides just IQueryable, have a look for your self:
来源：https://stackoverflow.com/questions/2681318/can-wcf-data-services-or-ria-services-be-implemented-with-nhibernate