Once you submit a sponsorship undertaking it goes to the local CIC office, which approves it in 30 to 60 days and then sends it to the visa post. From the visa post, they send out a form, the IMM 6000 package, which the refugee has to fill out and send back. When it arrives at the visa post, that is day one. If you consider that day one, then the average processing time right now is 37 months until the decision is reached.
On February 1st, 2007. See this statement in context.