Migrating from asp.net membershiptables to ASP.NET Identity

I was checking the ASP.NET Identity project http://www.asp.net/identity. I still have some questions on the actual features: I'm migrating from the older aspnet_users membershiptables with my existing site.
I was wondering if the new ASP.NET Identity allows my current users to connect via oAUth with their existing username/password? Also, upon migration, is the current userId preserved? Does the new ASP.NET Identity use the same logic for generating the unique userids? So is it again a field of type uniqueidentifier? I'm apparently not the only one with migration issues (Migrating ASP.NET SQL Membership to ASP.NET Identity with Database First), so I want to be informed fully before starting this process.