If they're coming from the same place, they would have the same vibrational frequency and it would probably be slightly different from the one here. At least that's a theory. Quinn talked about it once upon a time.
I mean... if the Timer we had was able to track the different universes that we visited - before it stopped doing that... we might be able to make some kind of a map based on the readings and maybe figure out if it's opening to a known-origin point before someone shows up.