From memory, if you place a storage bus from the network you want "master access" onto a ME interface of another, it creates a one way connection.
There was a way to do this without using the quantum bridges, because the bridges are very expensive, and are intended for long range connection, not simply across your base connections of subnetworks.
EDIT: tested this and it works, however to make sure that you're not transporting items into your subnetwork when you place them into your master one, set the priority of the storage bus that's facilitating the connection lower than your drive/chest, because it places items into higher priority first, then lower ones.
There was a way to do this without using the quantum bridges, because the bridges are very expensive, and are intended for long range connection, not simply across your base connections of subnetworks.
EDIT: tested this and it works, however to make sure that you're not transporting items into your subnetwork when you place them into your master one, set the priority of the storage bus that's facilitating the connection lower than your drive/chest, because it places items into higher priority first, then lower ones.