I'm not sure I buy the security aspect....radar heads are easilly spotted and not exactly hidden . The rotation speed can be measured by simply looking at the revolving head.
All the data seems to be available where wind farm assesment is concerned , so why the secrecy?
I suspect its more to do with the competition between major contractors.
The theory certainly seems to work for both Mode-S as above and Mode A/c , but it would be nice to be able to fill in the gaps.