Your breaks will always work, regardless of any electrical systems. You might lose boosters, but I doubt it, given that the car still has electrical power.

Some newer cars come with electrical parking break, and those will refuse to engage if you're moving. A lot of people in this thread seems to confuse this with actual breaks.

Mine has a "hold button for 5 seconds" type override - don't know if that's universal though.

Don't tell me it's the ACPI hard shutdown signal, that would be scary.

I believe you need to push the break when turning off a car with push button starts.