Simply put, yes you can. But possibly not easy to manage.
You can use pass-through authentication. Basically if a username and password are the same, then Windows will allow the authentication, even if the domains are different. So if you have a local user that is identical to a domain user, the user will be able to authenticate to either. As you can imagine, this may become a nightmare to manage.
Have you thought about WAN accelerators or WAFS devices on the remote sites to bring the central system closer?