s there any public information on actually how BERT is being applied to IR?

For each of the scenarios they described they are just like "here's potential hard search query, and BERT adds magic language understanding which makes it all better ". It's non-obvious how BERT is actually being used though, especially at the scale and latency they need.

(I get that that this is Google's "secret sauce" and they might not saying anything in this particular use of BERT. But I'm curious if anyone had seen anything related.)