Airplay does not work with Icecast?

When I operate Volumio with the output redirected to Icecast, then Airplay still plays to the ALSA output and the Icecast stream is dead during Airplay. I use a Raspberry Pi 2. How can I fix this?

I love VOLUMIO !!! And I love the Airplay feature.
Why do want to use this? My favorite use of Volumio is a central WebRadio-Server (95% of the time) and MusicPlayer (only sometimes) in the house. In our house I use several WebRadios, usually all of them playing the same station, often 3-5 of them in parallel operation. My music “follows” me through the house. To reduce internet traffic and to optimize simultaneous music playing, I use Volumio with a modified mpd.conf sending the output to Icecast, so that all web radios in the house use this stream.
I added autostart to the configuration, so that the stream starts automatically approx. 25 seconds.
In the original configuration, I loved the idea, that the use of Airplay interrupts other sources and when Airplay is not used anymore, Volumio returns back to play its playlist without having to switch anything. Brilliant idea!
The crown to Volumio would be, if narrow-streaming (intranet streaming) would be supported and Airplay would work with it!

Thank you for your help!

Does really nobody know how to redirect the Airplay / shairport stream to Icecast?
I searched all the web, but did not even find a hint.
Does anybody, that it will not be possible?