As discussed on au-talk.

All nodes are from the Overpass query:
node
  [highway=bus_stop]
  [network=Transperth]
  ["ref"~"^[0-9][0-9][0-9][0-9][0-9]$"]
  ;
out meta;

website tag added as 'https://136213.mobi/RealTime/RealTimeStopResults.aspx?SN=' with ref tag appended.