First of all, if we sell off electricity generating assests it is not necessarily to MNCs.
Prices would be reduced through competition. All producers would be selling the extact same product through the same national grid so therefore they are competing on price alone (there are no connection fees as you are already connected to the grid and nobodies electricity is superior quality to anyone else). The only way for the private companies to gain customers is to reduce their prices.
ESB Customer Supply should be retained and the government should issue licence for new Customer Supply providers such as Bord Gais and Airtricity. I have no prob with another semi-state body entering into other markets. For example Esat were dead against the ESB getting a mobile licence purely because it was a semi-state body. Semi-state bodies, local companies and MNC should be able to compete in the one market.