Your comment stirred an "ancient history of the future" type feeling for me. If the BART recordings could already be 50 years old (I doubt they are, but let's go with that for a minute), imagine that there's some speech recognition library being installed in some present day infrastructure project. Now imagine that module could sit unchanged, perhaps occasionally refurbished by historical technology preservation societies for hundreds of years until future generations look back on it like we might look back on city fortifications, aqueducts, cast iron bridges or Austrian Empire architecture.