Receiving signals doesn't. Advertising likely does. So if someone has proper equipment, they probably can identify the signals.

Ideal conditions is likely open spaces with no interference. Walls and concrete lower that as you mentioned.

I'm hoping it can help if people are standing right next to the rubble, whether BLE or the "siren" sound.

I have no guarantees though. I haven't properly tested because I haven't thought of a low cost option yet.