AFAIK, this is not possible - viewing the live image of the Blackberry with the playbook.
I think there is an application which makes the screen of the blackberry availible on the playbook using WiFi, but I doubt, that this will work reliable. Also, a dedicated camera is much better for this kind of task anyway.
you can: receive a webcam/ip-cam data stream with the playbook:
This can be done either using flash video or rtsp (flash is supported by the playbook native, rtsp is possible using an android application).
webcam + flash might need some amount of conversion. Most IP-Cams will send rtsp, but, not flash. Conversion can be done by using VLC and flowplayer software.
But also rtsp might involve transcoding video if the used codec by the Camera is not compatible with the playbook.
Or, just get a supported IP-Camera which works with the playbook. I would first go this way.
If you cant find anyhting, check out this post: rtsp playback:
someone will be able to help you to find the software and install it on the playbook. Then you should have plenty of choice of webcams which will work.