The bit across the river is only known at Butt Bridge and never Tara Street or Beresford Place.

Colloquially, people will say things like "Capel Street Bridge" or "Mount Street Bridge" for some Dublin bridges, simple because they don't know the name. This happens for a few Liffey bridges, but not Butt Bridge. It happens for many of the canal bridges. This is more an example of a metonymy or maybe loc_name=* and NOT name=*.

In Dublin, roads tend to change names at the rivers / canals, even if that change is as slight a change as Baggot Street Upper and Baggot Street Lower and hence the bridge does NOT have the name of the roads.