Having to declare a new agenda in Akonadi seems really convoluted (and not in any way obvious): http://forum.kde.org/viewtopic.php?f=20&t=90571 Reproducible: Always
Subscribing to a remote ical file is possible now through the (a bit obscure) way of "Add Calendar -> iCal calendar file" and then just pasting the http(s) URL into the file box. Although I think there should be a separate way to do this.