You know...........
I read that SXM devices can only receive and not transmit. So when you "activate" your radio all they do is remove one more identifier from the satellites continuous transmission where your radio just picks up if it's "authorized" or not to play the data it's already receiving. When you cancel your subscription your radio eventually picks up that's it's on the "kill" list and self deactivates.
This being said, yes, I have looked into this when I was wondering if it's possible to get SXM radio in my car for free.
What I DID learn is that it's possible no matter what radio you have. You just need a soldering kit and some type of computer chip reader/writer to reprogram it's identifier so that it never "sees itself" on that kill list so it just keeps playing.
There is a different method though. Since the satellite can only transmit so much data you can simply hide your receiver without powering it on for 6 months and eventually the satellite recycles your identifier from the "kill list" However, It could pop up back on that list on and off throughout time since it costs them nothing to assure that radios that probably already did get de-activated long ago are really de-activated.
Now, I'm not sure how much has changed from 3 years ago when I snooped around on this matter but that's my $0.02 on this matter