Beo would say no, because BM7000 is an audiomaster that is not N.MUSIC capable, because BS5 encore is an audiomaster too as a standalone product (for now). But it should work.
I would add an MCL2 AV box to MCL out of your BM7000, set BM7000 to A.OPT 0, MCL2 AV to L.OPT 4 and connect your Beolabs to Powerlink sockets of the MCL box. You can control the system as before, just press LINK - Source. For example: LINK - RADIO, LINK - CD...this will start the BM7000, BL4000 and selected source.
Now connect the Powerlink out of BS5 Encore to the second PL - socket of the MCL box. Pressing RADIO, A.MEM, N.MUSIC, A.AUX lets you control your BS5 encore and start the BL4000 without activating your BM7000. Take care that only one system is activated at the same time.
Or connect Powerlink out of the BS5 encore to A.TAPE2 socket of the BM7000. You will need a special `Powerlink - AUX`cable. For starting the system press LINK - N.MUSIC - source (of BS5 encore). Now Volume control works via BS5 encore.
NB: If you have a link system in the kitchen, BS5 encore can not be controled via link.
MCL2 AV is not in production anymore, but you can get one second hand. They are not expensive.
What is your TV? CD? "Another pair of Beovox? Extra speaker kit?
Hope this helps.
Stefan