Have you visited their website? Have you looked at the library or bookstore for books on the subject (fire trucks)? You stated you contacted the company, but have you tried contacting their field representative or dealer. Maybe the owners association?
I recently saw a coffee table book about fire trucks that was rather spectacular and indepth for under $20. Public librarys have many good books too...loaned free.
The internet and fellow forum members might have the resources you want, but there are benefits of researching for it yourself. Contacting the company directly may garner you the information you desire and sometimes a little extra cheese to boot.
I was asked once by a fellow IPMS member from South Africa who wanted information about the DC-3 conversion done by Bassler in Oshkosh. I made quick call asking if...what was a simple request turned into a very wonderful experience. Not only did I get the information I was after but also a tour of the facility, the oppportunity to take as many pictures as I wanted and needed, but the chance to meet and have as my personal tour guide, the founder of the company. That is the best cheese of all!
Granted I live close by, but on other qwests around the globe for information of various subjects I have been provided with the information I needed as well as program promotional items such as photographs, patches, stickers and toys to add to my collection just for doing a little old school researching on my own.
I wish I had what you were looking for...Good luck in your qwest!