If anyone is wondering about first reponders' use of land lines, that necessity is to be alleviated with the United States setting aside some spectrum in 700MHz back in 2012.

Do a search for "band 14" - here is something to look at: FirstNet

https://www.firstnet.com/coverage/band-14.html

[My household used to be required to have a land line ages ago and I still pay (slight) attention to things in this space. I do not have first-hand experience any more with such matters.]