I am retired but as I remembered a sprinklered building would get a huge discount, well over 50%.  I am tempted to say 80=90% but it probably wasn't that high.  If I was in insurance, I could easily prove it just by showing the rate manual page showing the discounts.  I no longer have access to that information. 

You don't think sprinklered buildings would get significant discounts?  We are talking huge value buildings and insurance being a competitive business will offer discounts which reduces loss exposure.  Sprinklers definitely do this.  They are definitely significant but more importantly may spell the difference between insurance at reasonable rates and no insurance at all.  I remember the Marco Polo being a difficult building to insure so I think it would be to their advantage to do it.  I have long forgotten the specific problems of its difficulty to insure.  I doubt it has changed much.