Hey neosphere,
Sorry for delay in response.
There was a pretty thorough response from Tim Sweeney regarding Windows apps that included a bit about Windows phone that you can read here:
portion pertinent to your question is this:
We have been doing some work in this direction (implementing various levels of WinRT API support) and we want to have Windows Phone support eventually, but we’re a very long way from having a ship-quality implementation. Right now our mobile efforts are really focused on iOS and Android based on their huge market sizes. We have a lot of work to do on these platforms before expanding to other mobile platforms such as WP.
Hope that helps!