First off, congrats on getting music to stream to your laptop. Not that I've been looking lately, but I did'nt know that any laptop bluetooth s/w had the correct profile to accept stereo data. What kind of laptop/bluetooth s/w did you use to get this working?
On to your issue, I would guess that it is the laptop that is actually answering the call. Perhaps there are some settings there to turn it off?
On the BB, under Bluetooth options -> laptop -> device properties, what services is it using? If handsfree is shown, you can try turning that off in bluetooth options.
I am also having this same issue. It only auto answers when the BT is connected to my laptop (also for streaming audio). I'm using a BB Storm. The BT is using a Broadcom 2045 chipset.
Options --> Phone Options --> General Optons --> Auto Answer Calls is set to 'Never' but it still auto answers but ONLY when connect via BT with my laptop