It is very likely that the ATF agent will win. Cops did not follow their own procedures.
Sadly enough, I believe you may be correct in that assessment. Not because the cops "didn't follow their own procedures", but because they followed them to the letter. Vindictively so, it appeared to me. The responding officer could have demanded and allowed ATF guy to present his credentials and warrant. But ATF guy took an attitude that did not play well. And he got smacked down when he would not cooperate.
The Feds do not like that kind of thing when it is applied to one of their own and they have plenty of ways to retaliate in kind to a local police department. The department will probably settle and cut loose their own men to deal with it by themselves.
The side with the most lawyers wins.
I do believe we got some outstanding entertainment from this episode. The price was a bit too expensive. My sympathy is with the locals.