The Citybus timetable shows as a footnote the cross town destination shown on through routes, mostly north-south cross town linked routes. Many of these are long established, eg Balmoral to Silverstream and Stranmillis to Cavehill Road. A bus coming from Balmoral will show 39 Silverstream all the way in from Balmoral down the Lisburn Road. I don't know of any operator in England which does this the same way - if a service goes across a city centre it will have the same service number on both sides, as is the practice in Dublin. Other services - Newtownabbey, west Belfast and East Belfast (except Cregagh) terminate at the city centre and buses coming in to town on these routes display 'City Centre' (except when the driver can't be bothered to change the display at the outer terminus).