As advised by some forum members here, I called the call centre again today and talked with a different agent this time. I was on hold for about 20 minutes, which isn't too bad. After looking into my application. the agent informed me that no decision had been made yet on my sponsorship application. He added that applications that have been submitted at the same time as mine are currently being processed and if I don't hear anything by this Friday I should give them a call so that they can 'take action'.
So, come Friday, if I or my spouse don't hear from CIC, I'll give them a call and ask them to take action.
This time there was no mention of the processing times being from when they actually start processing.