Google Calendar will not WorK or sync with Calendar.app after Yosemite or IOS 8.1.2
I was having the problem where a couple of events on Google Calendar simply did not show up on Mac Calendar.  I went into the event on Google Calendar and edited it - say, I changed the title slightly.  This somehow "flushed" the event through and it showed up in Mac Calendar.

I noticed this problem arose after I decided to re-link my Google account to my Mac since I was having issues with certain contacts not showing up when I wanted to compose a message in Mac Mail.  Per Google's instructions I re-introduced the Google account as a CardDAV account instead of simply as a Google account.  Not sure this has fixed the contacts problem but it did create the problem above with Calendar sync.

So for me editing the event in question fixed the problem.  But for the bigger problem described by @Michelle Wedd I do not necessarily have an answer.  Maybe she can provide an answer if she has been able to fix the problem.