This excerpt taken from the SIRI 10-K filed Mar 10, 2009.
Our broadcast studios, terrestrial repeater networks, satellite uplink facilities or other ground facilities could be damaged by natural catastrophes or terrorist activities.
An earthquake, tornado, flood, terrorist attack or other catastrophic event could damage our broadcast studios, terrestrial repeater networks or satellite uplink facilities, interrupt the SIRIUS or XM service and harm our business. The companies do not have replacement or redundant facilities that can be used to assume the functions of their terrestrial repeater networks. The companies do have redundant facilities that can be used to assume immediately many of the functions of the broadcast studios and satellite uplink facilities in the event of a catastrophic event.
Any damage to the satellites that transmit to the SIRIUS or XM terrestrial repeater network would likely result in degradation of the affected companys service for some subscribers and could result in complete loss of service in certain or all areas. Damage to our satellite uplink facilities could result in a complete loss of either the XM or SIRIUS service until the affected company could transfer its operations to its respective back-up facilities.