> There are already Eastern DC grid ties.

Strictly speaking there are only three ties into any NERC interconnection. Two of them are ties into SPP. The other is a single AC tie into SERC but it was only briefly activated after Hurricane Ike and hasn't been activated since.

This new project has ties being built directly to both MISO and SOCO which means the texas grid will be connected directly to two of the four main operators of SERC (the southeastern grid/power market).