One of the most commonly accepted trends in access networks evolution is merging access and metro aggregation systems, under the premise of enabling the cost-effective support of a larger number of users and/or an extended geographic coverage using a single physical infrastructure. This network architecture extends the reach of the transparent link between the end user and metro networks, providing savings in terms of the aggregation equipment typically deployed between the access and metro aggregation segment. However, bridging access and metro aggregation networks requires a careful dimensioning taking into account both the system limitations and the need to guarantee a low cost per user supported. This paper addresses the capacity boundaries of a metro-access system, formed by multiple tree-based high density access networks interconnected transparently via a high capacity metro ring.