The alien race is on a planet that has only been surveyed by the US and the UK is the only other power that knows the system even exists. There is a small US colony visited by the US Navy and a very occasional civilian ship. Considering the only way for the colonists to talk to the rest of the universe is via the jump gate network plus the importance of the information, I don't think controlling the information flow would be very difficult. That is assuming most of the colony is even aware of the existence of the aliens. A planet is a pretty big place. Besides, the Manhattan project stayed pretty secret and that was on the same heavily populated planet as many other nations, not twenty billion miles away with only a single communication link.
(and yes you may be taking it too seriously - I don't think keeping the Eben secret is the most implausible part of the AAR)
I think it depends greatly on your view of what actually happens below the game simulation scale.
If we for example assume the world is alive and buzzling with personal/corporate shuttles, yachts, small trade ships, small explorer & leisure ships that have similar range and speeds of bigger civilian ships it becomes a different matter entirely...
The implications is that any knowledge within the jumpgate network and not under strictly enforced military blockade is spread at minimum with the speed of the civilian shipping. Because thousands of civilian smallships, especially near the less policed and regulated fringes can land at a whim more or less where, how and when they want.
These would also be the preferred method of choice for espionage and eavesdropping on transmissions since as long as you don't have active emissions and behave within the expected realm of what civilians would do you won't be suspicious.
I don't think these assumptions are totally off. Translate the Aurora travel-times to current Earth and consider how many private jets, helicopters, yachts and smaller tradeships below the cargo liner scales that traffic our oceans and skies.
I know it's a big matter of personal taste, but when I RP Aurora I always assume everything within the jumpgate network is public knowledge of all races and factions that can communicate and trade with eachother.