There is another element here. The courts have ruled that police actions on duty and in public interactions are consider public and not subject to most privacy laws, including recording them without permission. This means that their actions can be recorded and broadcast (the very reason they are playing this music to avoid that). It shouldn't matter what the intent is if they are a public figure, then they should know that others can film them and that recording can be broadcast. So they know they are being recorded as a public official and that it could be broadcast to a wider audience. Playing a song to try to limit that broadcast is a completely illogical and stupid idea. If they didn't play it, there wouldn't be any copyright music to be concerned with. By playing it, they know this video could be broadcast on platforms or media that don't filter and that it absolutely, without question, leads to unlicensed reproduction.

Basically standards for public officials are different from normal people.