Sorry, but I don't think it is open to all as you say. It is open to all with the updated OS. For me it keeps saying that it is not avalaible for my device, whereas France is in the included countries. It seems that until our carrier pushes the OS update we'll have to wait...
Yesterday the whatsapp page on bbworld website 'listed' the countries, today its changed to 'all countries'
My carrier informed me today that whatsapp has been made available to bb's with os 10.0.9.2372 and lower, in Pakistan at least with the network I'm on. They also went on to say that the new os will not be available till later on.
I also went around yesterday asking friends on different networks on old bbs to confirm that they can see whatsapp in the app world and none of them did Today after speaking to my network I asked a few mates again and they all have access to it.
God knows what's going on.
I just hope we can all get it ASAP. I'm holding out for Monday.