Nobody knows. Microsoft's own release makes no sense. You (and your employer, combined) cannot contribute more than $18,000 tax-free per year. It's either 100% match of $9,000 on your $9,000 to make $18,000, or it's 50% match of your $12,000 to make $18,000. It can't be both things that the press release says it is.
My best guess is that they meant to say they now match 100%, but we won't know for sure until they correct the press release.