Do you wake up when there's an ambulance passing by while you're sleeping?
What if you change your statements to:
1) Detecting an abrupt change in sleep patterns in mammals is useful. 2) Dogs are mammals.
Therefore, detecting an abrupt change in sleep patterns in dogs is useful.
No I do not. This is why dogs have been used as sentries for thousands of years.
Just as humans, dogs go through sleep phases and even though humans have longer sleep phases; dogs have a REM phase. Once dogs get to the REM phase they're in a deep stage of sleep and the sound of an ambulance or foot traffic will not wake them up as easily as you think.
I've seen it hundreds of times throughout different breeds of dogs. I used to work part time for a vet when I was a teenager.