That ledge is actually accessed through a hatch in a conference room behind the camera. But they do still need a properly geared up person and may need someone from MNR to do it. From what I gather they aren't calling on MNR unless it's urgent due to the costs.
Actually, there is a peep hole behind the nest box and cameras in an equipment room. During banding, a few years ago, they accessed the ledge from the far end. No swing stage was used.