As long as you have the software upgrade from a couple years ago, it is my understanding that the wireless will support "Wireless ML" (although, you cannot connect speakers to the Wireless RX in this mode). However, I do not know if this allows for bi-directional audio (I think not since it was really designed for link room applications where the audio only goes one way, and one wireless is designated the transmitter, and the other the receiver - again, implying one-way audio) - that is, if you setup the BV7 connected to the Wireless TX, then you can listen to your TV through your BS5, but not the BS5 through your BV7.
Also, here's a very helpful link that lists the compatibility between the wireless and various products. I do not see the BS5 listed - it probably came after this list was generated so I guess we really do not know for sure.
http://forum.beoworld.org/blogs/coolskin/archive/2008/02/24/Beolink-Wireless-2-compatibility-list.aspx
Am I to understand that you will not be connecting the video output of the BM5 to the BV7? This will require a cable.
Stan