WARNING, when I did this the tablet crashed, on its reboot it was fine and talk was installed. I've copied other apps into this folder since and its not crashed so it could have been because I'd not re-booted after mounting root and system from the file explorer. Please don't blame me if anything is broken after this!!!
The only way I was able to install it was to download the talk.apk, I've uploaded it here
http://db.tt/WxnhGxuJYou'll need to get a file explorer with root access, I used ES File Explorer. Open the file explorer, then go to settings and enable root and system mount, I'd then re-boot. Then copy this file into \system\app
I also copied the two video chat files, into \system\lib
http://db.tt/Gqp8n1da Video Chat
http://db.tt/us7mJhVn Video Chat Stabilize
The video calls do seem to work if your calling out, but cant receive calls. I've not been able to work this out.
IM chat seems fine though.
There maybe a better way to do this, or safer. And It maybe that the video file should be somewhere else which is why there not working. Someone may know more?