The distributed k-mutual exclusion problem is to guarantee that at most k computing nodes can enter a critical section at a time in a distributed system. The use of k-coterie(a special set of subsets of nodes) is known to be a robust approach to solving this problem. In oder to evaluate fault-tolerance capability of such a k-coterie-based method, a generic measure called (k, r)-availability has been proposed. However, an existing evaluation method can be applied only to a special kind of distributed systems such that nodes are fully connected by completely reliable links. To cope with this deficiency, we propose a new evaluation method that can be applied to distributed systems with arbitrary topologies and unreliable nodes and links. To perform evaluation effectively, we introduce a new notion of r-Minimal Quorum Spanning Forest(r-MQSF). The (k, r)-availability can be evaluated by using these r-MQSFs. Then we conduct experiment for various systems to show the usefulness of the proposed method.