The event happened last November 1st in Hibiya, Tokyo, in which the three performed their respective transformation poses and later talked about their experience working on the Kamen Rider franchise. A similar thing happened last July in which the first three Kamen Riders appeared in the Kamen Rider Film Archive Special Night event.
Aside from the films mentioned, as part of the event's Kamen Rider 50th: Kamen Rider Anniversary in TIFF event, multiple Kamen Rider films from various events will play in said event in various dates. Some of these films are: Kamen Rider vs. Shocker, Kamen Rider BLACK: Hurry to Onigashima, Kamen Rider Decade the Movie: All Riders vs. Dai-Shocker, Kamen Rider W FOREVER: A to Z/The Gaia Memories of Fate, Let's Go Kamen Riders, and many more. You can check the full listings on the official TIFF website.
[additional info from Igadevil]