Yes, they work.
The amplification and clamping time is roughly the same across all the Pro Ears models. The NRR is higher with the Gold models, and there are features like a jack for an MP3 player. But the Pro Tac 200's also work.
If you are law enforcement, you would probably not want to wear ear plugs underneath the muffs as it would ruin the "hear the slightest sound" advantage for tactical work. Your selection would be based on how much NRR you want, balanced by how compact the muffs are. For example, the Gold models have a higher NRR, but they don't fold up as small as the Pro Tac 200's.
However, if you just want to hear range commands, this can be done with a slightly cheaper model with the volume turned up all the way, with foam earplugs under the muffs. You lose the ability to hear better than normal, and instead it seems about the same as no hearing protection at all.
Then, when the firing starts, the electronic muffs clamp to their 22dB NRR, and the ear plugs provide 32dB to whatever gets through. (The NRR isn't additive, but it is definitely more than either product used alone.)
The result is really kind of startling the first time you experience it. I found it makes range sessions a lot more pleasant. Instead of flinching when the .300 Win Mag next to you goes off, you just kind of ignore it. And you can hear the range commands. (Well, assuming someone isn't trying to talk at the same time firing is going on...they have to talk during a pause in the firing.)
IMO, it is hard to beat the combination of electronic muffs + foam ear plugs.
I got the Pro Tac 200's, but the Gold models are better (for a lot more $$$).
To answer your question about dead batteries, yes they just do their standard NRR. What you lose is the ability to hear normal conversations with the muffs on.
.30-06 Springfield: 100 yrs + and still going strong