I'm not sure how the trees will react to concrete dust. Its been a conversation in my area because there is a company out by Highway 99 crushing old concrete to make new concrete. One of the major concerns is the alkali in old cement reacting with alkali in new cement. Too much chemistry for me.
But when I read your post, I had a different concern. How windy is your area? Italian Cypress are cutting-grown, they don't have a tap root but do have a relatively small root system - they may have a difficult time staying upright in the Santa Ana winds.
