Yes, I've seen this happen actually. My Gyjga, Pretender, and a Skratti were attacked by an enemy Manticore--the AI automatically selected a pummeled the manticore with Stellar Cascades. It died shortly thereafter, so not only does it work, the ai will cast it automatically in certain situations.
It does not have a magic resistance check, but it is only armor PIERCING, not armor negating, so high Protection SC's will require more castings. BTW the pretender I was using was an Astral/Water Son of Nifel so he was also using Quickness
I don't remember if they Gygja also cast the spell, but it's certainly possible.. 3 Cascades/round would be very nasty. It also has a nice area of effect so you don't have to have great precision to hit and can be used by a good number of wizards from different nations because of its low level (2 Astral).