The official schedule on the WDW website just lists Epcot as a single entity, no separation of the two parts. To me, that means all of Epcot opens at the same time. I have read that the festival food booths don’t open until 11, though.
The pavilions will be open to walk through and the ones that have rides will have the rides open. Restaurants that serve early will be open. Food booths, stores, bars and most restaurants probably won't be open until later.