We did the Northern Europe (Baltic) one last summer--everything but St. Petersburg, Russia had free shuttles. So, Tallinn, Helsinki, and Stockholm had the free shuttles.
We only used the Helsinki one back to port after we had an excursion drop us off in the market square...so not sure 'where' the other shuttles let you off! Stockholm we had purchased the Stockholm card and just got on one of the HOHO buses that was right at the port. Tallinn, we had an excursion--but we did ask our guide where the free shuttle was, just in case we weren't done shopping by the meet-up time.