I just discovered that Plays Alto, Tenor And Baritone did see a digital release in the U.S., on this disc:
This disc is a "two-fer." It contains the entirety of Sims' Argo quartet session (Zoot!), but omits two tracks — even though they could've easily fit, but it's an Orrin Keepnews production, so naturally he had to tamper — from Plays Alto, Tenor And Baritone. The Fresh Sounds disc mentioned above contains all of Zoot! and all of Plays Alto, Tenor And Baritone. Jordi Pujol wins. Plays Four Altos, contrary to what I stated above, is on a different Fresh Sounds disc.