What's the exact effect of the security cameras in First World Bank?

Solution 1:

The Payday's wiki now has more information about security cameras in general (and I confirm that from my own observations):

Destroying the cameras will "Reduce police intel" on your team, which will make it harder for the police to group up and find your squad, as they are forced to spread out and search for you. More often than not, if you or your team is within viewing distance of a camera, they will home in on you directly.