I'm on a slab, the only way to secure the phone lines is through conduit and a lock box. It could be done... I probably should. I've thought about cell backup but I get discounted monitoring by doing everything myself. They don't take cell backup (or not DSC anyway)
You DO have a good point though. If I did have a crawl space where I could run the phone box into the crawl, I would. I wouldn't worry then. Even with a lock box and conduit, someone could circumvent by digging to get to bare wire. That may sound absurd but it would only take a couple of minutes. Maybe I over-think things. VERY few people would ever know to dig and find bare wire to cut.