just read this on ieee spectrum (Score 4, Interesting)

seems that recently a portion of the subway burnt down and when the guys went down to repair it they found that the hardware driving the system dated back to the 1930's. After more digging they found that the original systems laid in the early 1900's till 1920 were still operating and actually in daily use in many other parts of the subway. point is that thing is working well that they dont want to touch the thing. the other fact is that there is no way they are going to get the thing changed without majorly affecting the daily workings of the system.