Architecture – Plan Calls for Rebuilding Haiti Away From Port-au-Prince

From NYT: Architecture – Plan Calls for Rebuilding Haiti Away From Port-au-Prince

“the plan is built around a bold central idea: to redistribute large parts of the population of Port-au-Prince to smaller Haitian cities, many of them at a safe distance from areas most vulnerable to natural disaster. In the process the plan would completely transform Haiti from a country dominated by a single metropolis to what the planners call a network of smaller urban “growth poles.”
….
“This will only work if these poles become magnets of attraction — with agriculture, tourism, industry and especially jobs,” Mr. Voltaire said. “Otherwise, these people are going to come back.””

by doing so the planners are forgoing economies of agglomeration at Port-au-Prince. What were the positive externalities that led to massive growth there rather than elsewhere. Do they no longer exist? Can they be replicated elsewhere? Will government be decentralized as well? Will businesses move?