All satellite providers must now maintain EAS equipment, but are only required to pass national level alerts. XM has even been designated a level 3 entry point for EAS and is directly connected with FEMA, as a backup system to issue national alerts.
XM also delivers various weather alerts and Amber alerts on it's Traffic & Weather channels, as well as XM Emergency Alert 24/7 (XM 247). I am not sure, but I would guess Sirius at least passes local alerts during local weathercasts, but I don't think they usually play alerts on Sirius Weather & Emergency // 184 unless a very severe situation (Katrina and/or 9/11 level of severity) is happening.