Turn signal tap

[FredFishface]

Hi, I own a 3500 2017 Duramax but I believe the question is relevant to the 1500 series. I wish to tap into the left and right turn signal circuits to provide a trigger for a left and right side view camera. It appears that the X3 block on the BCM  has two relevant inputs (pin 12 and 24). Can I simply tap into each circuit before the pin? My understanding is that the turn indicator switch (S78) pulls the two BCM inputs low (to ground). Is this correct? Are they high (12 V) otherwise? Is there a better way of doing this? I want a constant trigger so I don't want to tap into a circuit after the BCM. If there is a better place to do this, please let me know. Thanks in advance.