The printed copy of the 1997 Cook County Building code is practically half advertisements. Its almost like "Oh hey, I see you are looking up requirements for fire rated doors - here are some fire rated doors I can sell you!".

In Cook County's case, I'm pretty sure the advertisers are politically connected.

Also Cook County's code is so damn asinine. Had a 7 building renovation where the owner wanted to put in a central laundry for all the residents, which was a vast improvement over the current laundry facilities in each building except for one. Cook County wouldn't allow it because they have in their code that each building needs to have a laundry room. So, we had to convert a unit in the building without the laundry room into a new laundry room. Fun times in Suburban Cook County.

post it! if not easily found will look for it and post when I can....if you look closely those NYC code adds are coordinated with the code section.

City of Chicago building code books from 2002 and 2010 (at the least) have multiple ads throughout them, also coordinating with the specific trades and code section you are reviewing.  Also, ads for various unions.

1973 City of Chicago Building Code and Contractors Register

according to that title it's blue book meets building code. 

Chicago - 1914

San Francisco - 1934

I find this interesting because this would be the same as if in the United States Constitution next to the Second Amendment had GLOCK gun adds or something... so far from my research only Chicago, San Francisco, and New York had codes with adds. 

I also found this while searching, not related but interesting -

The London building acts 1894 to 1905 (57 & 58 Victoria, cap. CCXIII; 61 & 62 Victoria, cap. CXXXVII. 5 Edwardus VII. cap CCIX.) With copious index, notes, cross references, legal decisions and diagrams, also the bylaws and regulations