I was testing out some things today. I did verify that getting the 3 Teddy Bears starts the Samantha's Lullaby, and I also verified that shooting off all the mannequin heads starts the techno song (not sure of the title). I also found that kniving the fallout shelter starts someone voice(s) but I couldnt understand what was said.
My original theory was that something would happen when you had the ticker at 00 (which means the clock is also at 0) but in my solo run, I couldn't find anything more after that.
Some other small things I noticed was that the electric power box to the right of the yellow house blows up when you shoot it, also the TV in the green house looks very suspicious to me. Also the hanging bicycle in the yellow house... whats up with that?
Also, after playing some more I did find the voice in the shelter varies. I heard a female voice saying something to the effect of "ugh, it's ruined!" and a male saying something like "that's not a reason to..."