I have this issue too and have an active subscription. Problem is people are getting PTR accounts locked to Cata, meaning they can't play 90's. I played Beta over summer after DS without live subscription, so it's not subscription issue.
Alot of other complaints on site are about "red servers" and build 5.05 (which sadly doesn't update automatically to correct version). This is because if you download PTR from your account, you basically get a build from September, because Blizz haven't removed it from accounts page. You have to go to client download list to download the 5.2 version. Unfortunately this means in my case I went through over 40 GB's of downloading to not even be able to raid test or play my 90.