I've not seen it from the inside like the Samba developers have, but I do work closely with them. Based on that experience, I think the relationship between Samba and Microsoft is complicated. It's true that the EU case forced Microsoft to release certain documentation. I doubt they'd have done it without that.
But, Microsoft did take somewhat of a "if we can't beat them, join them" approach to the situation, which I think was useful. I certainly still have a strong bias against Microsoft due to their past actions, but I don't think they've been completely begruging on this issue in their collaboration with Samba.
It's about their self-interest, though: Microsoft now needs Samba more than Samba needs them. They're still acting in service of their profits, but now their profit-motive is more aligned with helping Samba than it once was.
I was peripherally involved in that (my employer was part of the lawsuit) and Microsoft releasing the specs for RDP. It was somewhat encumbered which would have been hugely problematic for free software projects, but not for commercial entities (who I worked for).
I'd reverse engineered RDP, but that is way more time consuming than starting with specs. That work was put into escrow along with my papers, hexdump printouts with marker highlighting and scribbles etc.
Only one engineer was given access to the RDP spec which was kept in his locked office. Even the component including RDP was built by him in his office on computers in his office which were not networked.
I don't know if what we did was because our lawyer was too paranoid, or not paranoid enough!