What it looks like you're trying to do is go beyond market analysis and into industry analysis for your startup. Your market is much broader and includes your industry as well as your consumers and everything that affects both of those.

Probably the best way to get the information you want is to get a job working at one of those places for a few months. You will learn the industry inside and out if you keep yourself open to gathering information.

Another (probably obvious way you've already considered) is to call the companies as a potential customer. Ask them questions about their products/services that you would expect them to answer for a regular customer.

That should be enough to get you started. Good luck!