  We analyze quantum network primitives which are entanglement-breaking. We
show superadditivity of quantum and classical capacity regions for quantum
multiple-access channel and quantum butterfly network. Since the effects are
especially visible at high noise they suggest that quantum information effects
may be particularly helpful in the case of the networks with occasional high
noise rates. To our knowledge the present effects provide the first qualitative
borderline between superadditivities of bipartite and multipartite systems.
