My area certainly doesn't have any power backup for the CATV/Broadband. There have been faults in the area with loss of service when the powere supply somewhere along the network has died. That's not necesarily to the local street (my house lights stayed on), but somewhere maybe even in the next town through which my services get routed.
Simple really there is no SLA on residential services so no obligation on uptime. If you need guarantees you have to pay more for professional suppliers (and that's not Clara.net - see my other thread
)