From what we can see of the results of our jirachi findings, its easy to theorize that other events can be shiny as well. I asked many people (yamipoli, loadingNOW, gold ursaring, etc) why the B-A-C-D uses a restricted seed. Nobody knew, and now the discovery that its checksum base makes alot of sense. Checksums are ALWAYS different. Something as small as receiving a mystery gift, placing a pokemon, moving, etc.. will change the checksums in various areas. Each event probably pulled from one or more checksums (there are 8 for the primary save, and 8 for the secondary save). Once you get the pokemon and came back to the machine, your checksum would be different, producing a different Pokemon.
What is the likelihood of a LEGIT shiny event poke existing... probably close to zero. Is it technically possible... now we know it is.
With that said, that is why I put "Shiny Notification" so that people who are using legality checker to check for events are notified that most likely a shiny pokemon that is legit does NOT exist.
I would also expand this to include MYSTRY mew, since technically the origination seeds for all of the pokemon events COULD HAVE produced a shiny. Again its VERY VERY unlikely. There might have been ONE shiny mew buried in ALL of the cartridges.