We spotted this on our regular walk around the block:
The horizontal rails have a latching ramp that’s good enough in most circumstances:
Perhaps those latches released as designed under an overload. The snowplow would have been traveling toward us on that side of the road and pushed the snow against the fence panels hard enough to dislodge the rail latches from their sockets.
I suppose they can zip the fence panels back in place, one by one, without rebuilding the whole affair.