my thoughts on the subject are along the lines that the junkers were out exploring new places to gather junk, and found this massive mysterious minefield on the edge of sirius... so, they went exploring further, carefully wiggling their way through the minefield until they came to the other side and found an entire, undiscovered house.
They saw a business opportunity - obviously nobody else (or very, very few people) had ever gone through the minefield and survived the trip before, because nobody in sirius knew about this french house; so the junkers had an ability nobody else had, getting through the field with cargo, information, etc.
They found the proper authorities (probably the corporations first, and the government at a later date) and struck a deal to smuggle all this stolen technology through for the gallic corporations to reverse engineer and improve upon. The gallia government, ruled by a line of kings who want to invade sirius in order to avenge their ancestors that were left behind when the sleeper ships first launched, decided these junkers could provide information on sirius organizations/houses and thus the junkers became a valuable ally and agent for the crown.
not all junkers work for gallia, not all of them likely even know about it - more likely just a small group descended from those junkers who first discovered the way through the minefield.
Although I do like your story Tenacity Igiss had this to say:
' Wrote:Q:[/b] It appears that Gallia had an extensive espionage network in Sirius. Do we know anything about the spies? A: Espionage network was built by a well-known faction currently present in many areas of Sirius. This faction was initially founded in Gallia by a group of colonists who had anglo-saxon origins. Later, Gallic intelligence took the faction under close control. Presence of this faction was extended to Sirius, namely Bretonia and Liberty; nowadays, most members of this faction are completely unaware of its true origins and goals.