In a project like this the team gains a great deal of understanding about how the business works and there is always the temptation to keep that understanding within the team. The argument I have heard is that by keeping all the details hidden then the team will maintain control over the results of the project. What I've seen actually happen is that when a team tries to keep secrets others just don't believe them.
In the LTV project we made the decision to explain every detail to anybody who asked. The result was that people had a great deal of faith in what we produced. Even if people disagreed with the decisions that we made in the project, they understood and could respect the decisions.