With the recent merger of Sirius and XM they are now starting to combine and revise the station channels (for example all the "decade channels" - i.e. 40's, 50's, 60's 70's 80's stations is now a shared station between XM and Sirius - many channels are shared like this now). I would have thought this would not have affected the XM streaming methods on Soundbridge (other than changing the channel number in the soundbridge URL as applicable) but I guess some streaming protocols may have changed. XMstream.com does not work for me now either.
I do not believe there was ever any easy way to get Sirius to stream to a Soundbridge.
I hope a way is found to get XM to stream to Soundbridge again as this was a pretty nice feature to have (even though the artist name and song title never showed in the Soundbridge display when streaming XM).