evilducky,
Certainly an interesting question. Individual issuing bodies can obtain their own stats from Auscheck regarding turnaround times and data on a national level is also produced but not necessarily made public.
It is with Auscheck who collect the background checks from various sources where most delays occur. However the system is certainly a far improvement from the early days when it was a paper and post process through AFP.
In the grand scheme of things, I don't believe GA cadet programs would have a huge impact on the overall demand. I would suggest the totals would be a fairly low percentage of the numbers for industry as a whole.