This is probably the most foolproof. The fabric idea wouldn't be a good idea considering many public restrooms are multi-person. So the concern is with the privacy of others, not just the officer.
I understand that's probably a hard sell though, as people have some idea that it's verboten to record in the open space of a public restroom (it's definitely frowned upon, but I think police cameras are a good exception to have, especially if they need to enter the restroom to perform their jobs because that's where a disturbance is), so whatever gets more camera use in the end I'm on board with, from a practical standpoint.
They expect that the law should be followed, which stipulates no recording. Companies have tried for a long time to have security cameras in bathrooms, but it's not allowed. Now if they're responding to a call, then maybe that's an exception. Or they could change the law to allow recording in the bathroom, but there will probably be a ton of public pushback.
I think (but could be wrong) what most people actually care about is that their stall is private (or in the case of urinals, that someone isn't to the side recording what they consider a small private wall space area), but since that's hard to account for and some stalls/urinals already have poor privacy to the rest of the bathroom, we got what we have now.
Honestly, to me it seems like a lot of bother to hide bits of our body that we should all be a lot less concerned about shame about in the first place, but I'm not holding my breath on any change there in the U.S.
I agree with this, for many laws really.
If a man at a baseball game went into the restroom and up to the trough holding a smartphone that was clearly recording, he would undoubtedly find trouble. People expect not to be recorded in the bathroom.