This makes me wonder if you know what the purpose of design is.
It is to create the experience. Not create the possibility for it to happen.
It isn't "accidental" at all, it is designed. We create those "restricted" areas because we know how players behave. It is because we make those passages, that teamwork arises. So take Hurtgen forest as example, do you think it is an "accident" that those lanes are designed as they are? No it isn't, it's a well planned and more importantly, well executed design.
It's when the mapper have no clear design and just drops some controlpoints where he thinks it is fun to build one, that the teamwork - the whole game play - is "accidental".
We have this too in the mod, dont get me wrong here, Fh2 lacks in design on a monumental level, alot of the game play is purely accidental, or coincidental to be more exact, and many maps are knock-knock-on-wood-hope-it-works every time they come up on a server. Sometimes they work, sometimes not.
My point from a designer-point-of-view, is that it is our job to design Fun, Excitement and Teamwork, not the players. If we dont work hard to make sure those things happen on the maps, it's pure amateurish to hope that some players will gang up and go "hey guys, this kinda sucks, but it will be more fun if we run together and talk to eachother all the time, that way we can block out the fact that this game doesnt provide any experience itself"
So sure, chatting and VoIP:ing surely can save some boring game rounds, or make fun game rounds even more fun, but it's a "post-experience" function - an add-on - not part of the core experience. Because we cant guarantee players will use, we need to build in teamplay moments by design. (And yes; we have a long way to go there as well in FH2)
I would welcome suggestions on how to create more teamwork by design, not by rules (i.e. join squad or kick, use Voip or kick etc)
PS; this is a teamwork theory thread, I havent stated exactly how to improve teamwork, Im just stating my opinion on how to relate to it.