Hi,
Actually by downtilting you would be decreasing both cells’ coverage area and making signals stronger for the cells in its vacinity.
Now that the far off mobiles no longer camp on to overshooting cell site and would not be transmitting at high power to generate interference for MS camped on to the other cell being interfered. So both the cell sites would be contained in UL too that would be reducing the Interference noise floor.
Very effective in situation when using SFH like 1×1 or 1×3