Bridge will be an app you will have to install on your Berry and your PlayBook it seems. You will download it to the Playbook via AppWorld and then scan the barcode in the app with your Berry, thus installing it on your Berry. As for launch date, we are all still holding our breath (And about to pass out!). By March 31 is all we know in the States.
The latest info says the PlayBook will be released in March or April. I also saw a video recently where someone from RIM confirmed that the PlayBook will be able to Tether but it will be up to the carriers to decide how that will work.
