There's plenty of unclassified info available. Start here.[1] This is an overview document from Defense Acquisition University, a unit of DoD. It's a painful PowerPoint. You have to plow through a lot of really boring military documents to get the details.
EMP doesn't address small devices much. Small devices with no wires connected are not very vulnerable, because the energy is mostly at somewhat longer wavelengths, meters or tens of meters. Worry about cell towers, not cell phones.
Other than the power grid people, the civilian sector doesn't look at EMP hardening much any more.
The grounding is usually required to meet a standard and is tested during the towers installation. There are also coaxial surge arrestors and isolators that get used along the span.
Some of the site to site communications equipment has no ground component other than a PoE switch. The ethernet interface, radio, and antenna are all in a single packaged unit installed at height on the tower.
Communications equipment is not designed to withstand lightning strikes. Lightning protection is meant to prevent the tower from melting or the building from burning down, not to protect a receiver!
I'm not at all sure why you'd think that. Here's an actual product that sits inline with the coaxial cable and is absolutely intended to protect the receiver.
I did run through the whole thing. It doesn't actually say anything at all about what is or is not vulnerable, it's just a bunch of military standards and procedure about how to test for things and what to test, and some vague stuff about potential ways to protect things and what large military hardware they'd like to test.
Curiously, all of the links people have thrown out in this thread seem to prove exactly what I said - there's damn little available to the public in the way of documented experiments on real hardware for EMP susceptibility.
I don't have any really solid cites for it offhand, but it has been my understanding that small devices aren't vulnerable. I don't know EMPs specifically, but I have been involved in standard EMI testing for approval of consumer-grade electronics, so I know there's already a fair amount of testing for and shielding against EM interference with everyday consumer electronics.
EMP doesn't address small devices much. Small devices with no wires connected are not very vulnerable, because the energy is mostly at somewhat longer wavelengths, meters or tens of meters. Worry about cell towers, not cell phones.
Other than the power grid people, the civilian sector doesn't look at EMP hardening much any more.
[1] https://www.dau.edu/sites/default/files/Migrated/CopDocument...