What's the take on the Asarco - Southern Copper merger?

Grupo Mexico proposed combining their Southern Copper and Asarco subsidiaries into a one publicly traded unit. I've read a number of market analysts comments. One described the benefits of putting Grupo's mining assets into a company that can be valued separately from the company's railroad and oil-drilling operations.

Another raised questions as to whether shareholders would get their value by trading their Southern Copper shares for shares in the Americas Mining Corp, the Grupo subsidiary that controls Asarco. [right, credit Asarco]

Asarco is Tucson based. Southern Copper is Phoenix based with copper mining operations in Peru and Mexico. The Arizona Star lists Asarco's southern Arizona employment at 2,200.