Those antennas mounted horizontally rather than the typical vertical installation, are designed to optimize coverage for high-rise buildings, like skyscrapers. This setup can enhance signal propagation vertically, potentially improving coverage for users at different elevations in tall structures.
Operators are using this to take advantage of the smaller vertical beamwidth in order to increase the amount of sectors in a 90/120 degrees angle, without the huge interference from a normal 60/65 degrees horizontal beamwidth. By doing this they can have 6/8 sectors in 90/120 degrees angle and hugely increase the capacity of such location.
But still, keep in mind that configuration can lead to significant interference issues as we may have overlapping beams and increased cross-sector interference, which might degrade network performance. Proper network planning and interference mitigation techniques would be crucial to ensure this setup is effective without compromising signal quality.