Everyone understood that the job was not finished until the product was shipped. So virtually everyone, except those few scrambling to finish their parts, wanted it shipped because that was the measure of success. This permeates every project I have ever seen at Microsoft. No one has ever said that their part was done, so they've been successful. No one has ever considered their performance excellent if the project is in trouble.
People take ownership in the entire project.
Because people take ownership, they will step in and voluntarily help where needed. Since their job isn't done until the project is shipped, people with less work feel compelled to assist others with too much. And people pay a lot more attention to the entire project. If another part is in trouble, the sooner it is addressed, the sooner the project is back on track. Managers have to keep everyone on the project informed of direction and status.