It wasn't a unanimous opinion of the court, because it wasn't an en banc hearing. It was a three judge panel.
Boston could request a hearing by the full court, but since both the district court and the panel have already slammed them, their odds aren't getting any better by going higher up the chain.
This was an interlocutory appeal over immunity; the civil case itself is still pending in district court. As a civil case it doesn't overturn the law nor set precedent for criminal cases, but it does reaffirm what was already case law in the 1st Circuit: that there is a clearly established 1st Amendment right to openly record police, with or without their consent, while they perform their duties in a public space.