Where does the Route Planner get its data from?

Answer: 

The Portal utilities three data sets, these include government GIS data from the Public Sector Mapping Agency, Google Maps (including Street View) and the commercial dataset, NokiaHERE. There are data discrepancies between the three datasets and the ownership of roads (along with the name) can be updated by the Regulator and Road Managers in order to improve the integrity of the data set over time (this doesn't amend the source data, only the data in the Portal).