I am writing a piece where multiple seemingly disparate (even juxtaposed, without a common mission) government organizations are combining their efforts in somewhat of an unpublicized task force. This collaboration is not necessarily classified or secret, but it doesn't become known until when they make their bombshell announcement.
In a rare ______ of inter-agency cooperation, ...
What is a good word to describe this sort of arrangement that doesn't have the negative connotation associated with collusion?
EDIT: I'm looking specifically to include the unpublicized/secret aspect. Also, I'm not tied to a noun answer per se, other parts of speech are welcome as well.