WDM may allow this. I haven't tested yet though.
Nope. MC's WDM input can only play to a local soundcard or a DAC connected via USB or HDMI. MC has no capability to push WDM input to UPnP. Indeed MC has no capability to push any kind of external stream to UPnP, neither coming internally from WDM, nor coming from a cloud streaming service.
Matt has posted some thoughts about this, but it was deemed too difficult since i) the MC server would not be able to publish a ContentLength on an indeterminate length live stream, ii) there is no mechanism for a renderer and MC server to resume playing an indeterminate length live stream in the case that the Http socket drops (which it will certainly do at some time), iii) there is no way for MC to push metadata (e.g. file size, duration, etc.) in its single SetAVTransportURI call, iv) there is no mechanism to handle a renderer Seek request on such an indeterminate length live stream, (to name a few...)