A similar hijack will soon(ish) become impossible, as the current train protection system will be replaced by ERTMS.
Basically, the current system works by injecting a small current signal on one rail and trying to sense it on the other rail. A train's axle shorts the rails together, so sensing it means a train is present. Or, in this instance of sabotage, a jumper wire.
ERTMS L2, which is being installed over the next decade or two, primarily uses axle counters and train position reporting, so a jumper won't do a thing. You can still fool an axle counter, but that's rather easy to fix: just drive a known-good train over the section.
