It seems that rings and notifications are still played vie that phone speakers when BT headsets are connected. Some users see this as a flaw, I see it as a feature:
http://code.google.com/p/android/issues/detail?id=5634

If this is still the case with Froyo on the Tab, I'll just keep my BT headset in my pocket, and pull it out when I get a call (via SIP, no doubt). This also works for me when I'm sitting at my desk, or at home.