Strategically this is pre-positioning for a strike at IBM in anticipation of an SCO settlement, but it's also something else: a case of winning with the right hand, while winning with the left too.
That something else is simple: experience suggests that one copy of Linux in the hands of the Windows support group at a large company can vaccinate that entire company against Unix for many years.
How do I know this? I don't really: I think Microsoft has the research to back this up, but you and I don't - what I'm sure of, however, is that the experience among senior people I've talked to about this recently has been virtually unanimous: they brought in some Linux servers a few years ago -often on my recommendation- but even the units that made it into production roles eventually became problems, and more recent server recommendations by the IT professionals on staff have been going solidly Microsoft's way.
So who are these IT professionals? They're predominantly Wintel people who've gained credibility through face time with senior managers - face time achieved during crisis management situations I suspect were mostly caused by themselves and the technologies they espouse.