The Lead Encounter Designer, Daelo, posted the Raid dungeon testing schedule for October 19th. Beta testers in Europe may enter the Blackwing Descent at 11AM server time (PDT), and US players at 4PM PDT.

Blizzard Quote:
There will be two sessions, an EU session starting at 11AM server time (PDT), and a US timed session at 4PM server time (PDT). We’ll open the zones on all Beta realms (including KR!) for both sessions, and possibly longer.

The following encounters will be tested:

Maloriak in Blackwing Descent
Atramedes in Blackwing Descent

Blackwing Descent is a raid zone with an entrance located along the side of Blackrock Mountain.

Since these are the beta realms, this schedule is subject to change at a moment’s notice due to bugs and server issues. More raid tests will be occurring over the next few weeks.