"Bar" seems to come from "Barke", for barge, and my guess is that Barkasse, which is also given as "launch" (also a boat; see http://www.dict.cc/?s=barkasse), is the local Hamburg expression for tour boats or sightseeing boats, called Dampfer in Berlin.
After reading the website further, knowing that the intent is to translate it into English for tourists to use, it seems to me more helpful to translate the company name could be translated to something like "Ehler's Sightseeing Ships" (or boats or ferries) or "Ehler's Sightseeing Fleet", which would imply the idea of a "centrale" indirectly.