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!
Honestly, you'll waste your time. They'll see you coming from a mile away.
A fantastic source of market research is from larger public companies. Look up their most recent 10-K (annual report). They are legally obligated to give a fairly detailed market analysis (that synthesizes the research from folks like Gartner etc.) in each annual report. It's a great starting point.
Also, for most startup 'markets' there isn't actually a market. It's completely new. So 'market research' in this sense is not very useful and you should examine the premise that you need to do market research at all (versus say concentrating on whether consumers actually have a problem that you can solve).
Totally agree w/ nikiscevak. I abandoned one of my ideas for a wireless MVNO after analyzing the 10-K's of some publicly traded wireless companies. Just reading through the summaries will give you good nuggets of information.
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!