I’ve managed to make a short and hacky shell script that exports and updates a CSV file with the data downloadable from the AGL site, however I’m somewhat hesitant to post it publicly in case they block something as I rely on it for a few things 
Regardless, the data they provide is unsuitable for HA which is designed to log and respond to events as they happen. They seem to publish historical data at midnight each night, which means injecting the data into your HA database directly instead which is risky even with a proper interface (which HA doesn’t have for this).
I’m keeping an eye on a few threads such as this feature request, and this one, and this one… the list just goes on. If any progress gets made with those, I might improve the script and publish a plugin. Otherwise I’ll publish it if I lose access before then, as they’re definitely not the most cost effective provider for me.
Until then I don’t recommend holding your breath unless AGL releases a live API. Some distributors provide smart meter data that can be downloaded, although whether or not it is near enough to real time to be usable will vary. At the moment, Home Assistant Glow seems to be the best option for me at least.