I doubt it.

1. But he attacks from a different way. It's doubtful the Empire was aware of the Lete River escape route, especially since they'd just learned the whereabouts of the Returner hide out. If they knew Banon, Terra, and King Edgar (all of whom they wanted very badly) would have a back way out, they would have sent forces in that way.
2. Ultros is a coward. The easiest thing to do was to attack Celes. Attacking the others would be stupid, since he'd already been beaten up by them before. Attacking Celes was the best way to disrupt the Opera, as well. Something he expresses interest in doing.
3. Probably coincidence.
4. The Guardian has tons of different battle programs from non-Emperial monsters.