You'd probably assume if any, they'd be using the Entity Framework.
Anyway, looking at the comments in Scott Guthrie's blogpost (http://weblogs.asp.net/scottgu/archive/2012/08/28/announcing...) he also mentioned that they "will also support unstructured storage in the future so if you don't need rich querying you can use that too."
Also, from the comments he mentions they'll be publishing documentation for the REST API soon'ish (as well as "pre-built REST helper methods for Win8/iOS/Android/others").
We will also support unstructured storage in the future so if you don't need rich querying you can use that too.
I got excited for a moment. I've been using Azure for a few years now and I was thinking that this could have been a hint of them offering something more similar to MongoDB in the future. But, then it hit me that he's probably only talking about the Table Storage (Now called Table Service?) which I will never touch again.