I don't know what standby mode refers to, but I don't think it will work since the power needs to be cut in order to my power button to work.
When I press the power button the ATXRaspi will send a shutdown command to the RPi which will shutdown (duh). Then, the ATXRaspi will detect that a GPIO is low and will cut the power. When I press it again it will power it back up and wait for a specific GPIO to turn high to stop the fancy LED blinking.
So standby mode or any other suspend to RAM method will not work if I'm willing to use the ATXRaspi.