Well if you notice, the URL itself is pretty predictable. It's:
https://services.tcpl.ca/cor/public/gdsr/Gsdr[Alberta/Mainline][Metric/Imperial]yyyymmdd.html

Take special note that you cannot use imperial with Mainline. It might be easiest to just create your own interface and then build the url behind the scenes, so the only page you load is the one with the data. That seems like it would be fastest in terms of performance.