My understanding of "negotiating in good faith", is that it means both sides are trying to come to a conclusion that is acceptable (if not mutually beneficial) to both sides. It means they aren't going into the negotiations with a their minds already made up, unwilling to compromise some of their wants, to make sure both sides leave on better terms than they started.
When dealing with a negotiation between 2 sides that will continue to work close to each other after the negotiations, the aim needs to be as much about maintaining a good business relationship (based on mutual respect), as it is about getting what you want during the exchange.
It is similar in Washington. Often, the relationships built during the negotiations can be as valuable as the outcome, as each side learns more about the other, and gets an idea of where they'll stand on future issues.
Taking a "hard line" stance, and opening your position with a "bottom line", would not be in "good faith", as they show that side to be uninterested in making any concessions (which are a necessary element for both sides to be willing to consider, if the aim of the negotiation is a mutually beneficial outcome).