I have a 2014 Holden Cruze SRi here in Aus, and I've had 2 break-ins recently where the alarm didn't go off for either.
The car was locked on both occasions, with the red light on the dash lit up when the 'alarm' is activated.
The first time the doors and boot were left open after the break in, and the second time, the window was smashed and the rear door was opened to gain access to the vehicle.
Both times the alarm did not go off. Now i'm almost 100% certain that if the doors are locked from the remote, and the light is on on the dash, if there doors are opened without disabling the 'alarm' then the horn should sound, and the lights should flash. I'm pretty sure i tried this a while back, and that was the case, however recently it has not been the case.
Can someone shed some light on this before i go and chat to Holden?