Although confusing, that's the most interesting tidbit so far. Under what circumstances would they feel it necessary to take control of the Tower? What does 'a warded place' mean, and why speak in a guarded way?
I'd say the Reds might have immediately put this in place upon their joining of the Tower. We all know that nearly every Red considers their purpose the only worthwhile thing the Tower does so they likely only agreed to join the Tower at all because they couldn't actually stand against the power of the other 6 Ajah's. But, feeling that they were inherently superior they had their Grand Emergence in place should they ever need (or be strong enough) to take the Tower by force. I wouldn't be surprised if Elaida's coup was based on the Grand Emergence.
By "a warded place" I assume someplace in the Red section of the Tower they have built Wards with the OP that probably shield from eavesdropping and possibly keep out non-Red Ajah members in some way (obviously I'm guessing here) ... perhaps entering the room requires the use of a Red Ajah secret weave.