The spawns for VIP missions seem to be heavily scripted (ie, they drop in certain places, and immediately go into overwatch mode).
This means if you have people in the right place on the turn they drop, you can instantly kill them and be done with it. If you dont, theyre absolutely terrifying (they get off a reaction shot when you move, and then an additional shot on their turn. Thin men rifles are mean.)
Also, if I am not mistaken one of the classes has an upgrade for overwatch that allows them to fire when enemies move out to fire. I think that puts it closer to reaction firing of old, but I am not sure when or where that upgrade comes up.