John,
Unfortunately corporations look at this quite differently to smaller organisations and startups. Corporations tend to look at these things from a financial and maintainability point of view.
If the organisation is already locked in to a development stack/s, its usually quite hard to get them to buy into another stack. It means additional investment not only in developer resource but in maintenance (hosting etc), security and support.
It can be argued that the people pulling the purse strings in most organisations where this is not a line function, don't really care about the technology. In fact many eschew open source for the belief of lack of commercial support. Hence why Microsoft and Oracle, and Red Hat (commercial built on open source) are so popular in bug business.
Then there's the investment they've already made in hardware and operating systems. To have to support an additional stack and have staff that can intercept and support calls when something in a new stack goes down makes many a CIO/CTO I have met feel uneasy.
Fortunately with Rails, you might be able to get away with implementing on JRuby (hence being able to use their J2EE stacks) and using the mysql infrastructure they might already have.
You're probably in for a bit of an uphill battle. I think if you can convince them that your solution is superior in terms of overall cost and ease of use over another solution, you should have a win.
Happy to chat further offline.
Steve