You would need to be pretty close to the server/storage/etc to get a clean enough signal to be useful though. So physical security might be enough to protect against this type of attack. You probably can't just dig up the powerline outside and start tapping it thankfully.
Get a dirty pickup truck, a warning vest with the text "CONSTRUCTION" on the back and a pair of those laser device to measure out the land.
Then also put some shovels, pickaxes and other construction and digging gear into the back of the pickup truck.
Lastly, learn how to not behave like you're doing something forbidden or bad. You can try it out in less secured areas if you want to train up a bit.
Once you've mastered that you can drive up to any place and start digging. Nobody will question it.
The same is also true for IT security. Pentesters do that sometimes; walk into the bank, walk up to the manager office or similar, wait for a few minutes, then walk back. Everyone will now assume that you talked to the manager (provided they didn't see you standing there) and you can do things like "can I plug this USB stick in? I'm from IT and were updating the anti malware software in all branches." (that actually worked, there is a DEFCON talk somewhere)
So in conclusion; don't be confident someone won't dig up your powerline and start tapping it. Unless you have a habit of talking to the construction workers if they're allowed to do dig up the road.
