Not… entirely true. The Empire did indeed set a trap for Elson and his rebel fleet, but it was not at the location where the Imperial forces intercepted the Mothership. That ambush took place at Vorshan’s Rift- Elson’s ship, the Kapella, was among the few to escape the ambush intact, and he elected to flee towards the exiles in the hope of finding common cause with them (note: this info is from the Cataclysm game manual). Their avenue of approach to Hiigara had recently become known to the Emperor, and he had deployed his forces to intercept both the Kushan and the Bentusi, if they should attempt to make contact with the exiles again (which, of course, they did). The description is still in error, though- the Empire didn’t deliver Elson to the Kushan; he delivered himself and the Empire merely failed to stop him from doing so.
Elson is not, in fact, present in the playable area of the map until his appearance is triggered by the defeat of the heavy cruiser that approaches the Mothership from below. At that point, he and a dedicated force of Imperial ships pursuing him (these are also not present until the event is triggered) jump in and head for the Mothership.
My pet theory is that the rebel ships which appear in M16, representing the rest of the forces that escaped the Imperial trap at Vorshan’s Rift, were each assigned to search a different region for the oncoming Kushan fleet before they scattered, and that Elson’s was simply the one that got lucky and found them.
Edit Of course the wiki says something completely different. Doesn’t anybody read existing material before writing new content for this series? Yeesh…