Exchange 2013 in a workgroup

Hi All,

I understand Exchange 2013 has to be setup in a domain with AD.
We have 4 sites, each setup with local workgroups. Users logon to their machines with local admin accounts.

I know it would be nice to move all of the 250 users over to AD structure, however that isn't feasible at this time.

My question is this:
I need to migrate from a POP3 server, to Exchange 2013. Can I just set up the server (Server 2012 Std + Exch 2013 Std) as a DC + AD, but just that machine in its own domain?
Will the users be able to access OWA of that server from their respective workgroups? (I don't plan on setting up Outlook on 250 machines...)

Any advice is greatly appreciated.

Regards, Minty