There can be excellent teamplay on pub servers, fairly frequently also. The issue is, however, a combination of having a competent, strong voiced leader on VOIP, and good map design that promotes teamplay.
I'm a total Kriegstadt whore, so I'll use that as an example of map design that promotes team play. One, it presents both the attackers and defenders with a very challenging situation that basically requires teamplay in many situations to work. The Germans must constantly harass the Russian tankers and keep thier MGs fireing. Meanwhile the Russians have a pretty hard job where run-and-gun soloers will be cut down very, very quickly. Taking the Moltke bridge REQUIRES teamwork, and can never be even close to be taken without corodination between tankers, spotters, MG supression, and the occasional organized charge. This harsh gameplay leads to soloers getting very, very frustrated quickly and either shaping up and working together, or leaving. Luckily, most people stick around.
It's also good because, even though the map is absolutely huge, it keeps the entire team mostly in the same area. You're all attacking the same plaza, or trying to get down the same street. So simple orders can be quickly understood and reacted to. If you say "Machine gun, second story, far right" the tanker knows what you're talking about almost instantaneously.
In any case, the point I'm trying to make here is that map design can have a big influence on how spontaneous teamwork can arise. Maps like StalingradKessel, Danzing, BlackDayJuly, etc. are frustrating at times because it offers the players multiple cap zones to attack, rather than multiple paths of attack to a common cap zone. I think an abundance of active cap zones leads to a pub-server team getting dispersed as everyone decides which cap zone they "feel" like going after. A linear progression of cap zones may seem boring, but maps like Leningrad, Kreigstadt, or the latter stages of Berezina prove otherwise. In this way, everyone is working towards the same goal, but isn't overly restricted. A proper ratio of automatics-to-rifles is important also.
But yes, before this turns from a long post into a full blown rant, I'll end it there. Teamwork on pubs isn't just about players being morons or good team members. It's more complex then that.