Alpha ground plane - Engine 4

Hi Al/ Rich

Just been getting my eye back with rendering with having ago at one of the sketchucation rendering challenges.

I was trying out the test engine 4, but got no alpha ground plane shadow, it only seems to work with Packet mode and path tracer (image below) - is that right? I'm sure it used to work with all 3 but its been so long I can't remember.

Foggy version for fun or was it burn out?