It's not really a bug. When the pakset was founded, road catenary was used for tram rails, and trams were put in the road depot. Later, actual trams were added.
Since we don't have trolleybusses yet, there is no real need to delete the old road trams. You can expect them to be gone with the first trolleybus, or maybe even earlier since the catenary needs to be redone for the next version anyway.