For those looking to get on the 3.0.8 PTR you'll notice that the download links for the client at https://www.worldofwarcraft.com/charcopy/downloads.html point to a 3.0.1 version of WoW. This version is several months old.
However once you download the version above, run the installer, and then run the game you'll be presented with the requirement to download another patch. This patch will bring you up to the latest 3.0.8 version of PTR client.
To put it another way: the version you get from the official download page will be updated upon installation. Just because it's old doesn't mean it's wrong.
This took Alex Ziebart and I a bit to realize, and we wanted to be sure that we shared this with you right away. Enjoy your PTRing!
We should note that the server names are a bit odd right now, but Alex is on the 3.0.8 PTR with his character he copied over earlier.
Edit: Pukka clears up the situation a bit more for us nicely: "Unless you were in the beta, you will not be able to access any WotLK content (or characters above 70 for that matter). Also, on the copy page, PvE lands you on a Spanish PvP server, and PvP lands you on a US English PvE server."