For those that have never heard an IEM recording, I have a sample from a Jimmy Buffett show last summer. The quality is VERY good for an IEM, so do understand that these results are not typical. This is just an example of a good day at the races, so to speak.
Wow, that sounds MUCH better than I would have thought.
I am heavily invested into the radio listening hobby, but my interests lie mostly in the military and civilian air arena. It is illegal to decrypt encrypted signals. It is illegal to intercept portable and cellular telephone signals. That's it. Everything else is fair game. Once the signal leaves the transmitter, it belongs to no one. I'm not talking about the content of the signal. It is illegal for one who intercepts and hears a signal to discuss (share) that signal's content with anyone who didn't hear that signal. I know, it's arcane, but if I told my wife what I heard one of the Eglin AFB fighters say, I guess technically I have broken the law. It's all academic; if the military doesn't want me to hear something, they have the ability to encrypt the hell out of it.
I would guess that the IEM signals are NOT encrypted, just too much to deal with, so that makes them fair to intercept. Depending on the size of the band, you would have several different freqs to choose from, and then have to decide which was best. I don't know of any portable radio receivers that output in stereo, they may exist, so you would have to have an industry specific receiver- ie what the band has, and you would have to have the ability to search freqs.
As far as being locatable, I have a hard time believing that a receiver can be triangulated. Some of the radio equipment I have is referred to as "frequency counters." These are highly sensitive receivers that are used to detect low-power transmissions from radios. I have never had them detect a signal from another receiver. All receivers do put out a small oscillated signal, but to have band security triangulate that is sci-fi. I doubt that they have the resources to purchase and train personnel on how to use the type of equipment the intelligence community has for this type of thing.
I don't know how I feel about IEM taping, I would think you'd get better, more consistent results from mics. I default to the position that it is probably hurtful to taping. Just as with all technology, the ethics are the difficult part. I suppose if you couldn't get into a venue, it'd be a cool way to listen to a show. The band takes the risk by using the technology, just as I do when ordering gear online. Again, I'm not talking about intelletual property, just the signal.