How did the mage that cast control actions see the PC mage if he was in a van? In shadowrun there is a general, maybe not rule, but conceit that all glass, especially that in cars, is polarized to prevent exactly this sort of thing. Most high end buildings also feature polarized glass so passing magicians can't just lob spells at people on the other side.
As well, the PC mage should have gotten his conterspelling dice to augment that will roll. The only time he wouldn't would be if he was surprised. Usually hitting a magician with magic doesn't work out that well due to counterspelling and the fact that most magicians have a high will power.
Also, spells are limited in hits by the force of the spell. So the most hits, without using edge, for a force 6 spell is 6 hits. This would be resisted by the magician with body and counterspelling in the case of powerball.
Lastly I don't think you can use control actions to make someone cast a spell on themselves. You would need control thoughts for that. Magic is a mental exercise and there is no physical 'action' to control in it. Just like you couldn't make a hacker hack a system by using control actions.
So for future reference, the PCs and the NPC mage should have had a surprise check with the NPC getting a +6 die bonus if the PCs fail to notice him due to ambush. The NPC mage needs to see the target, and vehicles have polarized glass making this difficult. Unless the PC mage is surprised, he should get counterspelling for his defense. Spells are limited in hits, not net hits, by the force of the spell and Control actions shouldn't make a magician cast a spell on himself. You would need control thoughts for that.
But otherwise, yeah it sucks to get hit by magic.