Generally, folks choose to deploy web-based applications on Windows Server because they already have Windows Server. Selling them something that will only work on Linux is a tough sell, so a competition like this that seeks to show off how well PHP works on Windows should be another small step forward for all those small ISVs like Box UK who want to sell products written in PHP - provided Microsoft actually do something marketing-wise with the results.
His idea is to build a PHP/.NET tool that can act as a web services gateway. He's already started development and blogs about getting the environment all set up - Windows Server 2008, IIS7 and PHP 5.2.9 For Windows.
He's made another post with an update on his status - finishing out the development environment with PHP up and running, setting up a database, picking an IDE (Visual Studio) and setting up a version control system (git).