I don't know how this applies in Canada, but in the U.S. my Verizon plan allows me to setup 10 "Friends and Family" numbers, which are non-Verizon Wireless numbers (since Verizon to Verizon is free). So, if one sets their GV number as one of the ten, all calls made from your cell using Google Voice are totally free, no cell minutes used. You can use Google's Voice app to do this.
Similarly, if you set Google Voice to display your GV number on incoming calls, and NOT the caller's actual number, any calls received on your cell are also free.
That plan currently requires you to pay for 1,400 minutes a month. The 700 minute plan USED to give you five F&F, but no longer does.
We spread our plan over 5 people, which you would think would make a big dent in the 1,400 minutes, but with F&F AND with our two sons never making "calls", we barely hit 300 a month.