Nope, that's why you never seen an Arceus on the GTS under level 100. I think the people who made HG/SS assumed that Game Freak was going to release the Azure Flute, so they decided to program the event to be triggered twice (once by the movie Arceus and once by the Hall of Origin Arceus).
I kinda think they should have released a shiny Arceus on the supposed doomsday (Dec 21, 2012) for some reason. Of course, had they released the Azure Flute in Gen 4, then a shiny Arceus would be legally obtainable.
I'm sure they'll have events for shiny Genesect and Unnerve Mewtwo at some point. We almost always get all movie related events that were distributed in Japan.