I don't know anything about Sonos specifically, but I know a good deal about ISY.
Possible solutions, both require that ISY has the network module installed.
1) If Sonos has IP networking capacity. ISY can directly send network commands to sonos provided you know the Sonos command library.
2) If Sonos has IR capacity. Get an Itach unit and setup ISY to have Itach "shine" the IR commands into the Sonos IR port.
I don't have Sonos, but I do have a whole house music system and I use the Itach to control it via ISY.
Also, please note that these are both one way streets. There is no reasonable mechanism for ISY to receive acknowledgement of command execution from Sonos or to otherwise know the status of your Sonos.
