Don’t big companies usually have a CIO (Chief IT Officer) who can be fired for those cases? That said, Lufty probably just paid a lot of money to Telekom to get a redundant fibre connection and Telekom simply put all four fibers in the same conduit below that railway line.
The bigger problem is probably that nobody knows whats down there until you dig into it, since records are only kept within one company. In Berlin they just built the foundation for a new high rise building and afterwards discovered that they nearly destroyed the tunnel of an active underground line which now has to be repaired, stopping traffic in there for months, which is still better than nearly burying a whole commuter train in concrete.