You won't have to run the wires along the soffits (unless all the cameras are daisy chained or something). You should be able to just drill a hole to run the wire into the soffit, then mount the camera in place from the outside. While laying on your face in insulation at the very end of an eave is less than comfortable, it's not all that bad to reach in for the wire, and pull it back out to a more comfortable area. I would recommend investigating the eave from inside the attic first, just to make sure you have access to where you need before you start drilling.