Microphone Stereo sources are scene based too, and they are supported by the Nuendo panner and Dolby Atmos RMU.
An Ambisonics source is scene based too, it is just 3D instead of 2D. So i do not see why Dolby RMU could not process it in the futur, if they implement the Ambisonics to theater discrete conversion engine, like they did for mono, stereo or multichannel sources.