I have several Cyberpower 900 AVRs which I use with my computers. All of them can connect via USB and are able to use the CP software to turn off automatically. Ironically, my Cypberpower 1500AVR does not have a USB port. The new AVRT does. So, I have it connected via serial cable to my server. I have to say I have not used serial cables in a long time.
Anyway, the software does not all the UPS to connect with the server. Physically/electrically it does, it just can't manage the shutdown process. I am using a Dell 2900 PE with SBS 2008 SP1.