Radar is a critical component of Autopilot and every other automatic cruise control system to my knowledge. So it was almost certainly active. A Tesla with failed radar system would not allow the driver to engage AP.
See specifically at 2:20:22 [2]:
> We use that radar to annotate what the vision is seeing, the bounding boxes that come out of the neural networks, so instead of human annotators telling you that this car, in this bounding box, is roughly 25 meters away, you can annotate that data much better using sensors.
I take that to mean that the radar is used as part of supervised learning for updating the model offline, whereas just the cameras are used as input to the model.