Here's a suggestion: You may want to refocus your subject title search. I've spent the past four years managing a formal mentoring program in my organization, and the grapevine often comes up in discussions around "grapevine access" issues. As in, those with access to the grapevine possess power that those outside the circle do not.
You might also examine bodies of work around trust and communications dynamics among members of leadership teams. Whether an organization professes an "open" team approach, or practices something less desireable, all roads lead to accepted rituals of information sharing among leaders.