There is no "official" celebration at France for Bastille Day.
However, the CMs from France who work there often do something special ... a special ceremony or spontaneously breaking out into song (national anthem). The pavilion is sometimes decorated out with bunting and French flags also.
The pavilion in general will be a bit more crowded that day, by the way. You'll also notice people cheering during the film, and the CM introducing the film will likely put in a little Bastille Day "plug."
I've been to EPCOT on Bastille Day a couple of times and I had never really seen any sort of big celebration. I was hoping there would be since years before I was there for Norway's independance day and they had a mini-parade with all the Norway cast members waving Norwegian flags on a festivly-decorated double-decker bus to celebrate it. I guess they don't do things like that anymore.