They did do this latter. In the press release which was read on the news article announcing Bord Gáis' entry to the market, the ESB said that they couldn't reduce prices because they were set by the regulator. They had some FG politician on to point this out as well, but 90% of the article was given over to the Bord Gáis cost saving. Awful journalism as per usual for this country.
soccerc's points are spot on. But most people won't look into the reality of the situation and will just boggle at the cheek of the ESB. They just want something to moan about. The best thing for electricity prices in this country would be to go back to having the ESB as sole provider and feck any pretence of competition.