It seems better to be careful:
From Microsoft Printing House - Font Distribution Frequently Asked Questions
Q. What can I do with the fonts that come with Microsoft products?
a. Fonts are subject to the same restrictions as the products with which they are supplied. You are not allowed to copy, distribute or reverse engineer the font files. For more information, see the license agreement that came with the product.
There is an option to embed fonts:
Q. Can I embed Microsoft fonts in my documents?
a. An attachment allows fonts to travel with documents. Most fonts distributed with Microsoft products allow embedding. To check font permissions, right-click the font file and select Properties.
I strongly doubt that they are distributed because the font is considered as embedding them in the document, because the font resource is loaded completely, as a separate object. I would still check on MS first, especially if you have any noticeable exposure (big company, etc.).