Google Calendar does not understand associated email addresses from Google Accounts when it comes to invitations.
Background on Associated Email Addresses
Long ago, Google enabled "associated email addresses". These allow you to map other email addresses to your primary Google account. This has multiple benefits such as allowing you to login to most Google applications, even Google Calendar, with any of the email addresses you have associated with your account. When you setup a new alternate email address, you need to go through the steps of validating the email address and clicking through on a verification link sent to that account.
When you check your account and have setup alternate email addresses it will look like this (my actual accounts are blacked out here but you get the idea):
As I said, you can login to your apps by using the primary or any of the alternate email addresses and it works fine. That is, until you receive a gCal invitation sent to one of those alternate email addresses.
Google Calendar Invitations Don't Recognize Alternate Email Addresses
At work we happen to use MS Exchange instead of Google Apps. I'd prefer Google Apps, but that is not my call. So, we make the best of it we can. However, I work with outside vendors who do happen to use Google Apps for their businesses. When we schedule meetings, such as for a screen sharing conference call, I'll often receive a calendar invitation from the partner/vendor, etc...and it will have been sent via Google Calendar. Of course, being work, they will send it to my work email address. For this example, let's say it's email@example.com and my primary, personal gmail account is firstname.lastname@example.org.
The problem happens when I want to see details inside the calendar appointment. In Outlook, I receive a the invitation and I'll see in the detail something like this:
Often the dial-in and screenshare link information are included in the details of the appointment. However, when I click "more details >>" I am given this wonderful screen:
Remember, email@example.com uses the exact same Google Account as firstname.lastname@example.org. As far as access to Google Apps is concerned, these should be considered aliases and I should have equal access. Unfortunately, it does not recognize that email@example.com is a valid and verified email address for firstname.lastname@example.org (and vice-versa). It it were smart enough, it would let me see the event because they both belong to the same Google Account.
Perhaps this is just an edge case and that is why the bug persists. Nevertheless, it is a crap user experience and Google should fix it.
So, Team Google Calendar, please fix this. We'll give you a +1 for it.