Never heard that any company from Big Five consulting firms asked to sign contract that does not allow to work for there clients or even for other consulting firm. In contrary this is the most logical and common move for consultants. I would say this is industry standard. They try to keep people paying good salaries, providing training and guarantee for future. What do you get signing this contract? In general NSC will own your life. They do not need to pay you enough because they know that you can not accept work in the area where you live. You have to move and this is much more difficult decision.