Sprinklers and Enlargements

Wondering if any owners and/or architects have resolved an apparent contradiction between the 2014 Building code and the oft cited Fire department rules. This is in regards to adding floor area to a single family home, with not change in use, exiting or occupancy. The FD cites as a trigger to use sprinklers on sub-standard streets (typical situation): ? There is an **increase of more than one hundred twenty-five percent (125%) in the square footage of the floor area of a building (excluding attic, basement and cellar space, as those terms are defined in Section BC202 of the Building Code) http://www.nyc.gov/html/fdny/html/firecode/faq.shtml But the building code specifically says in Section 901.9.3 no sprinklers are required in enlargements in single and two family homes (assuming no change in use or occupancy) for prior code buildings. No mention of narrow streets here. We are proposing a 130% plus horizontal enlargement of a single family detached home on what appears to be a narrow street. We should be in the clear regarding sprinklers with the exception of this contradiction. Any experience regarding DOB enforcing this fire department rule. The blog suggest the DOB ignore other FD recommendations. I also ask because another project I know of was hung up for over a year while trying to avoid sprinklers. It was a two family wood frame row house with an extension exceeding 125%. Thanks**