Where does all the raid information come from

Since the release of Ulduar, I find myself pouring over all the available strategy guides, watching videos, then applying it to our own nightly raids. We wipe, we make adjustments, keep some of what works, throw out what doesn't, and make up some of our own stuff based on what classes we have available each night to raid.

My specific question is: Does Blizzard tell top guilds like Ensidia anything about how the fight is supposed to work on the PTR?

I know Boss abilities are datamined and the lore behind the characters can lead smart people to reasonable assumptions about the boss abilities, but do any of the PTR guilds go in there with any knowledge or hints from the staff for making testing easier? I ask this because it seems like if Blizzard wants to thoroughly test the encounters and get as much feedback as possible, it would seem like the most likely method would be to provide a basic framework for the fight, then let the guilds figure out positioning, class assignments, DPS, healing, etc.

So how much does a GM from a guild like Vodka or Ensidia know when they're walking into a new PTR raid like Ulduar? How much is from assumption, how much is speculation, and how much information is provided by Blizzard?