This was as quite interesting experience, so here is a little braindump from me.
In many companies a huge amount of time is wasted by fear and politics. That can range from fear about the own job, the position to things like “watermelon reporting” (all green on the outside, but don't look inside). All this interferes an open communication.
Effective teamwork needs trust and trust brings saftey which leads to a more open and therefore efficient communication, because if you trust each other, there is no more any need to question everything oneself or the others have to say, there is no need for politics and fear. This saves time, increases bandwith (by exchanging meaning and not just information). You also have more options in situations where you have to decide about things, because one knows about the otherwise hidden knowledge and skills of the other team members.