The alarm was installed in our house 7 years ago. A few times the alarm went off. They called us. However, I do not know how fast. I estimate that it took good several minutes before they reached us - calling home first followed by a cell phone call. However, I never did a test so I am not sure.
However, the monitoring fees are high with a renewal every six months. I just happen to look at monitoring fees in Ottawa and they range from $14 - $20. I currently pay $25/month + HST.
Note, that my 5 years commitment is over and the company has not changed the rate.
I will call them and then probably shop around for cheaper rates.