pass it into an iCal parsing library for your programming langauge of choice
Which is what any calendar system does (like google calendar) when you feed it the iCal URL.
Which evidently does not appear to be the case for google cal - it converts these timestamps neither to UTC, nor to the timezone set in its own settings. Not sure why - as there’s no reason for it not to, and plenty for it to do so, but that is evidently the case here, as shown above. ¯\_(ツ)_/¯
I suppose I will search for a suitable lib then.
Thank you.