So far as I can tell this has never worked. Others have mentioned it as well.
Short description of error
The Wireframe Input node for Cycles does not work with Bump or Displacement.
Exact steps for others to reproduce the error
The attached .blend file has two node chains in the one material. You can switch between either chain to see the results by clicking either of the 'Material Output' nodes. Both fail to produce the desired results.
A solution to this may be similar to https://developer.blender.org/T43651