They’re separate thoughts that are inconveniently in the same paragraph.
There’s nothing wrong with defense making this argument, any competent attorney would do the same.
This case generally should be subject to prosecution because the raid is so blatantly corrupt.
City prosecutors can absolutely sue city officials though in cases like this, they normally get a special prosecutor or someone from another jurisdiction (like the county or state) to avoid the conflict like you said. This records act has nothing to do with criminal prosecution, it’s about public disclosure. A prosecutor can just get a warrant. This is happening because the news organization is requesting the messages.
That law doesn’t mean that every public officer’s phone is an open book, it means that anything a public officer does in their public capacity on a private device is still subject to normal public records disclosures. You don’t get the entire phone, you get the public records (the relevant messages).
My guess, though I don’t know, is that the news organization has to somehow establish to some degree of confidence that there are public records on the personal phone, which I’m guessing they’ll be able to do.