To the best of my knowledge, the B2 can share its own drive so that other devices (e.g., computers) can see its music directory, but cannot mount or map a drive from another device that happens to be on the same network. Out, in other words, but not in.
The description of what you want to do sounds like a Sonos system -- which can play music from any network-attached storage that supports SMB version 1 -- or something similar would be a more likely bet. The Brennan devices are really meant for playing back music stored on their own internal drives.
I hope that helps -- m.