I'm having the same problem. Shared calendars seem fine, it's Subscribed calendars that show up but don't have any events (e.g. something I've subscribed to read-only with a webcal:// or http(s):// URL.

The same was happening with my Google account on the iPad though, so I think it's probably a Google problem, rather than a Harmattan problem.

Switching my iPad to use MfE fixed it.

But switching to MfE on my N9 just gives me my primary calendar (and no amount of fiddling at m.google.com/sync or google.com/calendar/iphoneselect seems to change that behaviour :-(