Question: I've been able to add a Google Calendar (CalDAV) account to OS X Calendar (v6, Mountain Lion 10.8.5) without problem, and all my own calendars show up.

Is there a way of seeing calendars others have shared with me (these show up under 'Other Calendars' in the Google Calendar website settings)?

(Same situation on my iPhone.)

Answer: 
Yes, this question is answered by google here: 

<https://www.google.com/calendar/syncselect>

You can click on the link and select shared calendars you wanna sync with your device.
You could use a Calendar Program like Informant for macOS. it allows you to combine numerous calendars into a single app.