It's worth noting that, while the ROM agent aboard the
Outbound Light had prior knowledge of the Hanseatic League, the remainder of the crew did not. For their own reasons, ROM saw fit to keep this awareness of the Hansa's existence on a strictly need-to-know basis until after Operation REVIVAL.
Also, it's worth noting that a number of the places detailed in
ISP3 had been discovered by the Explorer Corps prior to their becoming known to Interstellar Expeditions - though, as with the Hansa, it's quite possible that ROM was very selective in terms of who, if anyone (even within pre-Schism ComStar), they shared this information with at each point in time.
It's interesting that, while the Explorer Corps sought to expand the DRUM network into the coreward Deep Periphery in order to support JumpShips with mobile HPGs operating in the region, they never went so far as to offer HPG service to the locals themselves. Not until the arrival of the Goliath Scorpions would the first HPGs be built in Nueva Castile - and not until after the Hanseatic Crusade was waged would the first HPGs be constructed in (now-former) Hansa space.
Although, had either ComStar or the Word of Blake offered to build HPGs in the region, might those have been affected by the Blackout along with their Inner Sphere and near Periphery counterparts? Or, might they have escaped the effects of CLARION NOTE, the way the Scorpion-built HPG network has done? It's interesting to consider a "what-if" version of the Hanseatic Crusade in which the Hansa had a ComStar-built HPG network, which might - or might not - have been forced to deal with the after-effects of Gray Monday.
And, as a further aside...
Everyone here understands that the Explorer Corps and Interstellar Expeditions are very different entities.
Not anymore, they aren't!