Cloud resources are increasingly pooled together for collaboration among users from different administrative units. In these settings, separation of duty between resource and identity management is strongly encouraged, as it streamlines organization of resource access in cloud. Yet, this separation may hinder availability and accessibility of resources, negating access to authorized and entitled subjects. In this paper, we present an in-depth analysis of group-reachability in user attribute-based access control. Starting from a concrete instance of an Access Control supported by the Azure platform, we adopt formal verification methods to demonstrate how it is possible to mitigate access availability issues, which may arise as per-attribute criteria groups are deployed.