Kind of funny how your statement is the exact oposite of the famous open office idea: "we have a flat mgmt structure and desks in an open office so the collaboration and free flow of ideas can occur!"
SHARED BUSSES!?!?? Wtf! Do we want tech employees sharing ideas and getting poached?!?! What is this communist Russia???
Uh. I want free flow of information inside the company, or of certain kinds of information between companies (or company and general outsiders). You absolutely do not want to share your most sensitive company discussions with your direct competitors. There's also some information which is regulatorially or legally sensitive and can't be shared outside the company before "everyone" has access to it.
Another source of daily irony is I dislike open plan offices in general as a developer; I'm now more a product manager (although I do tech stuff as well, and conference papers, and such), which is a role which does strongly benefit from open plan, and I've also we've built monitorhenge at a pod of desks in open-plan, out of Seiki 39" 4K and portrait-mode 24" U2410 monitors. It's essentially a re-creation of my favorite work environment; a private office shared with a small team.
Google doesn't actually run the bus themselves; it's Bauer.
(I hate the SV culture of having sensitive meetings in public cafes and restaurants, especially ones frequented by all your most likely competitors! Internal compartmentalization is also a bad extreme, but having a hard "insider vs. outsider" boundary, and then specific short-term projects with their own borders, and all communications about those happening in secure spaces, is my default.)