Well, the Caeliar were never willing to kill to further their own interests before; the furthest they'd go is to relocate individuals who threatened to expose their existence.Because the other Caeliar had a big part in that as well. I don't understand why it should be so hard to believe that these other Caeliar may have evolved differently just like the future-Borg Caeliar. Does it contradict future stories or something? And didn't these Caeliar end up being sent even further back in time than the Borg-Caeliar did? Plenty of time for a race to change its priorities.
Sure, it's possible. It just doesn't seem probable. They would have had the full resources of a fully-inhabited entire Caeliar city-ship to build upon -- very unlike the unfortunate residents of Mantillis.
But these Caeliar were in an older and more wild universe where they incountered who knows what. Plus with the Caeliar in the present for all that claiming to preserve life stuff, you would think at some point the Mantilis Caeliar or any of the Caeliar having known a lot about the tech in Columbia would have bothered to mention that the hyperphasic radiation in their subspace tunnels would have killed the crew. Which since they can't be that stupid would mean they have no problems not warning people that they are going to fry themselves. Not to many steps from their to frying someone else to survive.