Actually in my case, using the bt400 volume in live TV mode, it adjusts both the buzz box volume and at the same time changes the TV volume. After a while, while changing the volume, the TV volume becomes too loud (gets out of sync) and I need to lower it manually using the TV remote.
Interestingly when I use the vod and use an external player, like MX player or VLC, the buzz remote adjusts only the buzz box and leaves the TV volume alone.