Voice telephone, aka Plain Old Telephone Service (POTS), uses such a low data rate that it is broken up into digital packets and stuffed into the data 'holes' in other internet traffic.
SpyNavy
Garde la Foi, mes amis! Nous nous sommes les sauveurs de la République! Maintenant et Toujours!
(Keep the Faith, my friends! We are the saviors of the Republic! Now and Forever!)
LonePalm, le Républicain du verre cassé (The Broken Glass Republican)
“ ALL phone traffic is digitized, again with the exception of the ‘last mile’.”
Correct. And it’s the last mile that’s the easiest to hack into. A couple of alligator clips a bit of wire and a telephone handset and I’m listening to your conversation. Easy peasy. It’s not unlike installing an extension in your house.
So not only can you hack into a landline phone conversation remotely once it’s been digitized, you can do it locally with very primitive technology. In addition, since the land line is stationary, you always know where the connection is located, unlike cellular which can hop from tower to tower across the world.