Hi Tom,
Thank you for the response. The documentation which is the same for SCOM 2007 still says "Discover the Netbackup server as a Network device" as I stated in my origional post this is not possible due the way SCOM 2012 handles discovery of windows servers (it filters them out of network discovery). Which means that this method will no longer work.
The fact that I am seeing many posts in this regard and no one can confirm that they have got it to work is a concern.
I've opened a case with Symantec to see what they say but I would still like to hear on the forums if anyone has successfully implimeted this.