Yes it is possible to ejaculate from continuous testicle squeezing. I have experienced it while my balls were trapped in a homemade Humbler. I added a third dowel and compressed the testicles extremely tight. After trying to walk with it on, I ejaculated without stimulating my penis.
The ejaculation was as others mentioned, not very pleasurable. The cum just kept jerking out in a greater than normal flow. It was very arousing and I did fund it enjoyable.
I have also experienced an ejaculation with the teticles wrapped tightly in an Ace Bandage. The pain was steadly increasing after 10-15 minutes to an unbearable point, when I had an ejaculation. Also was not very pleasurable but was still fun.