Internal iOS update server for iPads (any/all iOS)
Yes - both iTunes and the Apple Configurator act as a single download point that can then apply one update over USB to an unlimited number of iOS devices.

No - iOS devices do not apply for OTA updates from any update server in an analogous manner to Lion's SUS.

It is notable that Mountain Lion is announces to not ship with a SUS and instead have updates arrive from the Mac App store - so Macs are becoming more like iOS rather than the other way which seems to be the foundational premise of your question.