1) I can absolutely see this as a plot hook for a few different scenarios. The most obvious that comes to mind is a servitor of Technology who's running a live field experiment. There doesn't even really need to be a reason –*that's just the sort of ridiculous, dangerous thing with that seems to have "potential" that a mad scientist would do. And then phase 2 of the experiment is testing whether the constant background hum is enough to get away with breaking stuff or killing humans.
And "breaking stuff" suggests another potential setup: servitors of Theft using it as a cover to get away with breaking and entering.
And come to think of it, since disturbance can muck with the cultivation of tethers, there are a lot of superiors who could have a potential interest in intervening here....
2) I tried using the disturbance rules as written for a long time, but found they didn't really work for my purposes. In addition to just being extremely precise and fiddly, with lots of modifiers to contend with, there's nothing really built into the game to prompt the GM to decide "somewhere, someone's making a disturbance" unless that's already written directly into a scripted plot hook. And if that's happening, I wouldn't make anybody roll at all –*I'd just tell them they sense disturbance, if that's a clue they can't really afford to miss.
By the end of my time running In Nomine with rules-almost-as-written, I was just calling for an unmodified Perception roll whenever I thought a PC might hear something that I knew was happening somewhere nearby, but the story didn't require them to hear. (This is kind of like the "Simplified Disturbance" variant described in the Game Master's Guide, except that I did describe disturbances' loudness to impress upon the players the difference between "that might have been essence spent on a song!" and "a demon prince just showed up and killed a bunch of humans"). That worked fine for my purposes. I used basically the same rule when PCs made subtle disturbances and I knew NPCs were nearby; just gave the NPC an unmodified Perception roll. When the PCs made exceptionally loud disturbances, I used the "Who heard that?" table (Game Master's Guide p. 124) to determine whether NPCs I hadn't even invented yet might have picked up on all the ruckus.
These days, I don't run In Nomine as written, but I have still run some stuff in the setting using other systems. For instance, I hacked Lasers & Feelings to make something that is obviously inspired by In Nomine, and is easily adapted to run in the same setting (
https://drive.google.com/file/d/1CDB...c77ihSS5u/view). In systems like that, a failed roll isn't just a whiff, but something that triggers a complication in the story. So, if you do something that causes disturbance, and you roll a failure at or right around that moment, the GM gets to pick whatever "something goes wrong" consequence they want, within the realm of reason, and "somebody in the neighborhood hears your disturbance and shows up to investigate" is a good go-to for that situation. I really like this approach because it give a lot more flexibility to introduce plot twists when they feel right in the story. If the PCs make a big disturbance, but we're pretty close to the end of our allotted time and I don't have time to introduce any new NPCs, I can just decide the ramifications will be felt later, when they have to report back to the boss who heard they failed to fly under the radar.