On Demand Migration for Active Directory is architected to prevent data commingling by logically separating customer data. Customer data are differentiated using a Customer Organization Identifier. The Customer Organization Identifier is a unique identifier obtained from Quest On Demand that is created when the customer signs up the application. This identifier is used throughout the solution to ensure strict data separation of customers' data.
Customer data is further separated as customer related services are isolated from any other OS process by the Microsoft Service Fabric exclusive process model. See https://docs.microsoft.com/en-us/azure/service-fabric/service-fabric-hosting-model#exclusive-process-model for more information.