I've been doing some research on this myself and I've come close, but I'm not 100% there yet. Here's a sample URL of a mobile "share event" link:
http://www.google.com/calendar/gp#~calendar:view=e&bm=1&action=TEMPLATE&text=Halloween+Party+2011&dates=20111101/20111202&details=Description&location=Millennial+Media&trp=false
It opens up the mobile version of Google Calendar and pre-populates it with details about the event your sharing.
The only problem I've encountered is when you're not already logged into Google Calendar. It takes you to the log in page, which is fine, but then after you log in it takes you to the home screen instead of the event entry page.
If you find or already found an answer to this, let me know.
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