If they're land lines, the NPA/NXX will be local to the CO so you won't have out-of-area numbers other than a rare corner case of a very expensive foreign exchange line. If they're VoIP lines, the address is *supposed* to be so registered, but softphones and even VoIP handsets tend to move around without the user considering 9-1-1.
VoIP was dragged kicking and screaming into E911, so now they charge extra and are quite clear about it. My VoIP provider regularly reminds me to update my 9-1-1 address, but since I don't have to pay the 9-1-1 fee if I lie and say I'm outside North America, that's what I do. Since I also have a classic CO-powered copper landline (1/4 mile from the CO, no concentrators or repeaters) and a couple of cell phones, I think we're covered. R's, John