There is no such possibility. As a workaround, you can install an instance of Adaxes service and Web Interface in each site. In this case, the Web Interfaces will connect to the closes service, and the services will connect to the nearest available DCs, making password change effective immediately.
The Adaxes Services, in their turn, can share a common configuration. This means that you do not need to configure each service separately. A change in the configuration of one of the services will be replicated to the other ones immediately. Also, when configuration is shared, you can use one license for all the service instances that share the configuration. For information on how to share configuration between services, have a look at the following help article: http://www.adaxes.com/help/?HowDoI.Mana ... ation.html.
Finally, you can configure your DNS so that all the Web Interfaces have the same address, but users will be redirected to the necessary Web interface server depending on which site they are in.