Superservers is a good company for what I know. Some companies separate their power and network uptime SLA, so technically if they have power issue but their network or part of their network/core router is still up then their network would still be 100% although power can directly affect your server. I am sure that they can work with you.
Respectfully, you are confused. Read their SLA and see how they calculate downtime. Scheduled downtime is normally not counted as downtime and 99.9 is NOT the best you can do. Telco's routinely measure uptime and try to acheive "5 nines" 99.999 uptime. Circuits go down all the time areas and nodes go offline but if the class 5 switch doesn't go down unexpectedly then they are still ok for uptime.
It is almost impossible to measure it to the individual server level if you are DC as there are too many variables. Customer reboots the server or initiates a power off via the remote power box and then what? DC's will pretty much always only SLA to what they can control. The core router(s) is a good place to start.