Okay, that explains where 11 comes from for en-banc...
But, today's 3-member opinion then has 2 that are not one of those "active" 11 - they are listed as currently being a "Senior Judge". That would mean that the en-banc 11 would NOT include two of today's judges (one voted for, one against; the third is one of the "active" 11).
United States Court of Appeals for the District of Columbia Circuit
https://blogs.law.harvard.edu/billofhealth/2014/07/22/how-en-banc-review-would-work-in-halbig/
The active judges of the court, PLUS any senior judges who sat on the panel, sit if the case is heard en banc. That means the judges listed above plus Randolph and Edwards, who both were on the panel in Halbig.