It seems that it’s currently impossible to determine who is streaming to a shared channel using the Authorized Broadcaster feature. I tested on my own channels and it appears as if the https://api.twitch.tv/kraken/channels/<mysharedchannel> endpoint does not include any information on the authorized broadcaster streaming to that channel.

Is this something in the works or planned? It would be very helpful for building extensions and bot commands for shared channels.

Note: when adding an email address to the authorized broadcaster list, it does check that the email is associated with a valid Twitch account, so this information should be available already.