They can get the info just by asking the lord. Would any lord really tell the banker "It's none of your business"?
as mentioned, they don't have to ask anyone anything. that info is shown to every single noble in the same realm already. you just have to go the extra mile to look it up in infrastructure tab of region details.
heck, it's shown to foreign nobles who happen to wander through the region or scout it
for all i know.. advy might see it too. haven't played an advy for a while. esp. not in testing.
basically.. not having it wouldn't stop a banker from ordering anyone doing anything.
