Not quite. The triptych Polyvision sequence is in Act IV on the third disc of the set (from about 26 minutes on). The different panels are included as playback options on this third disc; as such one would need three copies of the movie to play back the different panels. (The three discs in the set are Act I on disc 1, Acts 2 and 3 on disc 2 and Act 4 on disc 3. Note that this set is Region B and as such requires a region B player or some way to remove the region coding.)
I don't think that is correct. He would not need three copies, just three players and TVs. Each section of the tryptich is on a separate disc. From Chris Galloway's review at the Criterion forum:
The coolest feature, though, are separate presentations for each panel of the Triptych sequence in full high-definition: Disc 1 presents the left hand side, Disc 2 presented the center, and Disc 3 presents the right-hand side. Each is presented in the 1.33:1 aspect ratio. While the center frame is presented in a standard way with the image aligned horizontally to the center of the screen, the left panel is aligned to the right side of the screen and the right panel is aligned to the left side of the screen. I’m not sure if this is why they put each panel on each disc, but if you had the equipment (three television screens and three Blu-ray players) you could play the full Triptych sequence across three screens. Even if you can’t do that it’s great just getting the full blown frame and it’s fairly fun to watch each panel on its own.