I successfully added my Evolution (desktop-based) calendar events to my Google calendar with a few very easy steps (see below). To see how to view your Google Calendar from Evolution, check out Johnny Jacob's fantastic tutorial Johnny [Life & Code]: Google Calendar in Evolution. Got me fixin ta git me summa them screenshots an' purty up my page. Geez, Johnny. Make the rest of us look bad, why don't ya!
That said, the standard protocols and an API for Google Calendar already exist, putting the pieces in place for an update for Evolution popping up in our respective package managers in days, if not weeks. Should I be predicting wrong, then I challenge all the sharp hackers out there to turn away from Unreal Tournament and WoW for 10 minutes and bring your prodidgious grey-matter to bear on what would seem such an academic exercise in coding. Imagine, fifteen minutes of lightwork, and the love, admiration, cell numbers, IMs, MySpace pages... of the world will be yours. Think about it!
As always, Peace & Blessings.
(Now more than ever!)