The obviously missing third top line is the one that broke. It simply snapped around the middle of the span between that pole and the pole that is outside the photo on the right. They went up in the cherry picker, cut the dangling line, and then put on those clamps.
They then covered the lower arms of the pole with orange sheets: https://i.imgur.com/zZ3DFSd.jpg
Does anyone happen to know what the orange sheets are for? They did not use them anywhere else where they grounded the wires.
The place where they put these orange sheets in your photo looks like a disconnect switch between the wires on either side of the pole. So the wires coming from the left side of your photo are still live, and the disconnect switch itself is still live. Since they would be working near the disconnect switch (to hang the new wire), they put these insulating orange covers for extra protection.
The lineworkers I've seen that aren't working with live wires use a special tool to ground the wires (it's a set of three clamps connected by a thick wire to a grounding rod). Once the wire's grounded, it's going to be hard to put any voltage on it.