We are looking to integrate multiple web apps that utilize standard feeds (XML/ICS), but do not support multiple feeds; hence, we need you to combine our 55 calendar feeds into a single feed of some sort (ICS/XML, etc.). For example, our website will take an ICS feed and export the data onto our website's calendar.
It does need to pick up changes to any form of event (single, multiple day, multiple time, repeating, weekly, annual, monthly, yearly, etc. <-- all), including deletions, and so we're not simply looking for a nightly export or something of that nature. User should be familiar with the in's and out's of the latest Google Calendar API (3?).