In another HN article comment someone mentioned that it took Google Brain over a year to replicate the DeepMind AlphaZero code even though they are part of the same company. Yeah, I think there are barriers to communication there.
Also JAX came out of DeepMind and is being used by Search even though TensorFlow came out of Brain, moved to Core, and is being used everywhere else.
The first time I was at Google (~2010) you could send an e-mail to any engineer in the company and you'd get response offering to collaborate within an hour, and usually a CL under review by day's end. The second time I was at Google (present), it takes multiple quarters to get teams that report up through the same director to agree on who's doing which work.
Google Brain and Deepmind? Not sure about the "no comm" part, but their HQs are in different countries.