Just completing this thread.  I did test this today - connecting a 
BeoLink Active to the ML port of a BeoLink Wireless1 receiver, and it 
all worked fine.  On/Off, source selection, timer function, PC input, 
etc. all worked 100%.  The key is to not use the PL ports or IR port on 
the wireless.
Why would anybody want to do this?  My assumption is that if one 
device works, then multiple devices will also work (ML is a passive 
network, only the "master" really knows what is connected).  In this 
way, I can add an Active (currently sitting idle) to replace what I'm 
currently doing with the wireless (with the added feature of the PC port
 to support input from my non-B&O TV), and then add a Passive to 
drive some outdoor speakers... right now, I'm driving the outdoor 
speakers using a PL to RCA cable (from Sounds Heavenly) from the 
wireless into an old integrated amp, but I must disconnect my indoor 
speakers (BL4) when I play my outdoor speakers because, otherwise, they 
play too loudly when I turn up the volume loud enough to drive the 
outdoor speakers.  
Yes, I could probably accomplish most of this with a 2nd wireless RX 
(minus the PC port capability), but given the challenge with getting 1 
wireless working consistently, I'm afraid that a 2nd might interfer with
 the 1st as they would be mounted near each other.  I guess if I can 
procure a wireless cheaper than a passive, then maybe that will guide my
 direction...
Stan