Lists can currently be read by outside discovery systems (I am assuming this is how Aspen can import current lists from Koha), but there is no current API path to allow lists to be managed centrally through Koha. Once Aspen imports the lists, they are two separate lists. I would like to see API enhanced to allow discovery systems to work in tandem with discovery systems, so those systems can work together and the lists can be maintained in one place.
*** This bug has been marked as a duplicate of bug 27603 ***