In the UK we call this a PEN conductor fault. It's called a PEN conductor when it's used as a combined Protective Earth & Neutral, as in a TN-C-S earthing arrangement. The property earthing is bonded to the incoming neutral cable before the consumer unit ("fuse board" / breaker panel). This relies on the fact that the neutral side of the supply transformer is itself earthed (this is why it's called neutral; its potential with respect to the earth is ~0V). If the neutral supply to your property is broken, then the return current will pass through the internal neutral wiring in your home, back through any protective devices like breakers and RCDs, and then jump across your earth bond, back through the earth wiring in your home, and then to e.g. a water line or gas line bond, or in your case, coaxial; through the earth itself, and then back to the neutral side of the supply transformer, completing the circuit.
This has 3 important implications:
1) The return conductor (e.g. coaxial cable) may not be adequately-sized to carry the current you're asking it to, but your circuit breakers are rated in relation to the fixed internal wiring of your property, so they won't trip. This risks melting and subsequently breaking the conductor, leading to:
2) The exposed metalwork in your house becomes live. Screws at lightswitches, metal ceiling lighting pendants, copper water and gas lines, the works. All of it. This leads to:
3) An RCD (GFCI) or a device that contains an RCD (like an RCBO) will not save you when you come into contact with any of it, because the current is first passing back through that RCD on your internal neutral wiring, so there is no current imbalance from its perspective.
So yes, very dangerous. In the UK, we use concentric cabling for our street supplies, so it is very hard to accidentally sever the outer neutral conductor without also severing the inner line conductor.