I haven't worked directly with Microsoft for well over 15 years, but this sounds similar to what I remember. Back then I worked for a partner who was doing direct integration work against low-level SQL Server and Windows libraries. Often when we encountered obscure bugs, they'd just give us the SQL Server or Windows source code and basically say, "Fix it, and we will release a hot fix." All of the comments would be replaced with white space which made things more difficult.
But the point is you need to already have a relationship, right? It seems you can't just say "I'm curious" (or even better, "I want to track down X bug") and expect to get source access, contrary to what was claimed earlier... Enterprise specifically says you need to "Maintain 10,000 Windows seats" which is not something a lone developer would do...
