[lotyrin]

A more advanced civilization will have gotten much better at avoiding the energy waste of sending a signal except to where they want it to go.

The Drake equation of detecting intelligent life based on their signal emission needs a few extra terms for accounting for energy efficiency or perhaps even deliberate discretion (https://xkcd.com/1377/).

If we did pass through their data laser or whathaveyou, then perhaps it would be unintelligible encrypted information, but that's not something that seems likely to happen (even if things aligned perfectly, other star systems - particularly those with radio emitting civilizations - are probably too noisy to try to transmit through).

[norea-armozel]

The physics of electromagentism doesn't diverge all that much when you're talking about stray signals from alien satellites or radio arrays. So long as you use the radio spectrum to send signals out to satellites or interplanetary systems (probes, colonies, whatever) you're going to get spotted. Laser signaling may be the only alternative I can think of that wouldn't be so easily detected and probably lower power too, but that's it.

The only other alternative I can hazard speculation on is possibly gravity wave signaling? It's a bit of a stretch in my mind since the only real way to do that is to assume certain kinds of unproven particles like gravitinos (these are supposedly able to be interacted with in superconducting materials last time I read about them).