Strangely every report I see of this (also in e.g. Vietnam) stresses that it's due to the strength of the Nokia brand in these regions. A brand that Microsoft apparently didn't buy the rights to for use on smartphones.
e.g. http://allthingsd.com/20130903/microsoft-deal-could-mean-end...
"But when it comes to smartphones, Microsoft only has the right to use the Nokia name on Windows Phones that are in the market when the deal closes"