Ok, after TuneIn and Pandora, I can try to make things easy for Sirius too.
Please select a Sirius radio using the Sonos control application.
Then in the vera UI, reload lua engine (Reload button) and then when reload is finished, go to the Advanced tab of the Sonos device and tell me what is the value of the variable AVTransportURI.
I need the value of the variable AVTransportURIMetaData too. Unfortunatelly, the value is truncated in the advanced tab. So please run this code in the test luup box:
luup.log(luup.variable_get("urn:upnp-org:serviceId:AVTransport", "AVTransportURIMetaData", xx))
replacing xx by the id of your Sonos device. Then check the logs and copy and paste in the forum the XML file that was logged.