In this post Azret Botash talks about the OData WCF Data Service Provider for XPO.
The simplest way to expose your data as OData is by using the WCF Data Services, which currently comes with a couple of out of the box providers (EF, Reflection etc…). Each provider requires it’s own data model and if you have made XPO your ORM of choice, switching to another model is out of the question. Adding an additional data layer is not something you would want to do either, maintaining more than one is rarely a good practice.