They did for some things. There are several factions inside Microsoft, some more respectable than others . We managed to get MSRPC/DCOM documentation out of them no problems at all. TBH there was very little internal documentation on it apparently, most of it being inside 4-5 peoples' heads.
 Small note to IE team: fuck you. I opened a genuine defect with steps to reproduce on Connect 19 months ago which was a regression between IE8 and IE9 and it was canned earlier today with the old bug vs feature thing. This is after 6 months of arguing with PAID UP GOLD PARTNER support over the issue as well which fucked up any IE upgrade plans for our clients for 6 months.