From what I read on Aviation Week and Space Technology, the extension of the ETOPrule to 207 minutes is just restricted to the specific trans-Pacific routes. It will allow a twin (most likely a 777) to fly routes between US and Asia, when under extreme weather conditions, all 3 possible landing strips along the Alaskan coast are not able to handle a landing. The time required to skip these 3 potential landing strips to the next available airport is 207 minutes, thus the extension. Therefore, the 207-minute extension is not going to be commonly used as the 180-minute rule.
To Mirage: the 207-minute extension will not impact the A340 in favor of 777 as you suggested. This is because no airline flying between Asia and North America is choosing between A340 and 777. The extension is really to help airlines like UA to replace 747 with 777 on thin US/Asia routes.