Only the Federal Appellate court may call for en banc. In this case it would be 17 judges that comprise that district.
But the subject opinion is from the District of Columbia Court of Appeals, appealed from the D.C. District Court. That's my understanding; I'm not an attorney or an expert.
D.C. Court of Appeals Rule 35(b) states, "A party may petition for a hearing or rehearing en banc."
You are correct.