Alright i posted twice in the main thread and it seems people don't read the posts befor they go off talking about this and that.
As of now, befor BT patch you MUST kill the opera event to spawn the chess event. There is no question about it 100% proven fact. The reason this is now ineffect is because !legitimatly! you can not get to the chess event if you have not beat the opera and got the door open. I did this again last week its still soloable and all but you have to find a raid that has passed opera but cannot down the curator. The curator is the main boss that seperates your raid from doing shade of aran, prince, and chess.
Weither this will change in BT patch and they will just fix the walls and make chess spawn at all times again i do not know. But I doubt it reasonably, because 1 Blizz is lazy and doesnt like fixing invironment, 2 because what they did now is working, and 3 because they just made it this way and are to lazy to go back and change it again.
So as of now unless you can trick the system out thinking you finished the opera event (i think the chess is accually triggered by the opera event door opening when you kill them) your out of luck unless you can find a raid that did opera and doesnt have the ability or plans of doing the chess. and on the brightside, if you do find a raid as such, the sidedoor at the top will be unlocked if they pushed on to curator so rogues and warriors and others no need to respec or use auto unstuck anymore.