It would be the hotness if calendar could be shared in a CalDav format so I could sync to a R/O version on my iDevice.

Also, if you import the in game calendar in WoW to the website calendar, can it figure out if people sign up and sign them up here?

Sort of a "Oh look! Frommers signed up for this event in the game. I don't see him signed up here, but I do see a level 85 gnome mage named Frommers in the guild. I'll just sign him up here too!"

I don't know if that would change my signup routing, but it is a neat idea.

I'll look into the CalDav format, Thanks for the suggestion!

It'd be nice to be able to import the calendar into my phone as well

Is it possible to export the website events to the WOW calendar?

For example, when I run GETGRSSDKP it has the events and signups in it already. Can a /GRSS option be added to update the WOW Calendar with events that are not currently on there?

Unfortunately, no. It could maybe create the events and invite the folks, but it wouldn't be able to mark those who've signed up as having done so, so to avoid the confusion, I just straight up avoid it altogether.