Thanks for a bug report. Here [1] is a corresponding upstream bug. The change should be done upstream first, then possibly backported to the rebased version of evolution-data-server.

[1] https://bugzilla.gnome.org/show_bug.cgi?id=663828

Created attachment 1003349 [details]
eds 3.12.11 patch

Here's a backport of the upstream evolution-data-server patch for 3.12.11. Let's depends with this on the rebase.

Created attachment 1003354 [details]
eds 3.8.5 patch

And here's a patch for 3.8.5 of eds, for those whom do not want to wait for the rebase. I made a test build with it, which is available for download here [1]. It has some oddities, like when a Google account is added into GOA then evolution-data-server recognizes new calendars, but they may not always be populated straight away, thus it's required to restart background processes (basically the machine for lazy people like me), to get it fully working. I'm not going to spend any time on it, because the 3.12.11 doesn't do this (or I didn't notice it at least).

[1] https://people.gnome.org/~mcrha/rh1202372/

By the way, I was just pointed into the Google settings for the list of "discovery-available calendars" for CalDAV. That can be found at:
https://www.google.com/calendar/syncselect

as was answered at:
http://stackoverflow.com/questions/25669144/google-caldav-access-to-shared-calendars

to which I've got a link to from Erick, a gnome-calendar developer.

I made one more update in evolution-data-server, due to one change I noticed with the calendar discovery password (OAuth token) provide.

One more update in this regard, evolution-data-server-3.12.11-5, to have these steps working flawlessly (for company calendars):

a) gnome-control-center -> Online Accounts -> Add Google account
b) a page with Google login is opened, I filled in:
    User name: mcrha
    Password:  [left blank]
   then pressed login. That redirected me to saml.redhat.com.
c) on the SAML page enter my login: mcrha, password (pin + token)
   - I'm redirected back to the Google page where I'm allowing
   access to certain Google services to the GNOME project.
   After this the GOA account has its OAuth2 token.
d) evolution(-data-server) got the change and added enabled parts
   into the sources;
   * Mail fails with "IMAP disable" - bad luck, known issue
   * other services fail with "OAuth 2 authentication not supported"
   * Calendar (using CalDAV with the OAuth2 token, without giving my
     private phone number to the Google) works, I see my calendars
     in the Evolution

The change in 3.12.11-5 of eds was to not fail with authentication sometimes.

Yet another update for this bug report. This time should fix also the crash you experienced on the evolution-source-registry start. I managed to reproduce it with git master of evolution-data-server and backported the related parts here.

There is an issue that evolution resets the colours of calendars on restart. It should prefer local colours if set.

(In reply to Jiri Koten from comment #10)
> There is an issue that evolution resets the colours of calendars on restart.
> It should prefer local colours if set.

Fixed for Google and ownCloud discovered sources in:
evolution-data-server-3.12.11-7.el7

(In reply to Milan Crha from comment #11)
> (In reply to Jiri Koten from comment #10)
> > There is an issue that evolution resets the colours of calendars on restart.
> > It should prefer local colours if set.
> 
> Fixed for Google and ownCloud discovered sources in:
> evolution-data-server-3.12.11-7.el7

Unfortunately not, colours still get reset in evolution-data-server-3.12.11-9.el7

(In reply to Jiri Koten from comment #12)
> Unfortunately not, colours still get reset in
> evolution-data-server-3.12.11-9.el7

Ehm, you are right. Improper testing on my side. The ownCloud backend works as it should, while the Google backend doesn't. There was a fault in the new-source recognition, the Google backend thought that every discovered source was new.

I'll include the right change in the evolution-data-server-3.12.11-10.

I added one more little change into the package. it may not influence many things, but some corner cases only. The change is backported from the recent upstream changes.

To properly cover also in-evolution configured Google accounts with enabled Contacts/Calendars, a change from an upstream bug [1] was needed, thus I added it into the sources. Without it the calendars are not shown at all for Google accounts configured directly in the Evolution with checked "Add also Calendars" at the end of the new account wizard.

[1] https://bugzilla.gnome.org/show_bug.cgi?id=750148

I found another little glitch in the git master version [1], which is applicable here as well, thus I backported it.

[1] https://git.gnome.org/browse/evolution-data-server/commit/?id=0b20fce0b4444

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2015-2226.html