Why dont the terran fleet utilizes the vasudan beams? That would give all ships a definitive edge.
The technology is probably just incompatible (although the Deimos is possibly anomolous in that respect); for example, Vasudan beams could use energy conduits or cabling types radically different from those that Terran designers design for.
Or, Terrans just prefer green
Regarding the question of just how many refugees made it out of Capella, I seem to remember one of the briefings near the end of the campaign (in fact, it may have been the last briefing) stating that the evacuation was all but completed at the time of the supernova. Didn't one of the convoy members in the last mission say that their few ships were the last of the evacuees? I also seem to remember Petrarch mentioning something about most of the inhabitants of Capella making it out safely in the ending cutscene. I was always under the impression that the vast majority of that 250 million managed to make it out of Capella before the end.
2nd last
The majority of the fleet is fending off a massive attack at the Vega node. Thousands of civilians await evacuation and the enemy continues to flood in from Gamma Draconis. We will not get a second chance to pull this off. If we fail here, we unleash the Second Shivan War. We must get the Bastion through at any cost.
last
The Security Council has authorized the deployment of the GTD Nereid. The destroyer will depart from the Vega system and collapse the node in fifteen minutes. We must therefore complete our evacuation of Capella by that time. Any ship that remains behind will be trapped with the Shivan armada.
I used to be quite convinced that millions died in Capella. to be fair, I do have the defense of no wiki to check at that time
The 3rd last brief also indicate Capella is Terran, which also answer that question.