The community managers showed up on the PTR on Friday, and as you might imagine, chaos ensued. Eyonix appeared as a level one gnome, and he and Tseric both got invited to a player guild, where they chatted with players for a couple of hours. I don't know if any actually battleground matching systems got tested (that was originally their reason for showing up), but apparently lots and lots of people got killed by Gruul, Baron Rivendare, and even Nefarian appearing in Lower City Shattrath.
Hopefully a CM event like this (as has happened before, when the expansion beta ended) signals that the end of the PTR (and the patch going live) is right around the corner.
Gallery: CMs ingame