JSCL - the question you're asking is about what policy the Govt should take on competition issues.
On the one hand, you could argue that Govt should take minimal involvement, and let businesses get on with making money. Great for the shareholders of the businesses, but in most industries one usually finds that companies merge and you end up with one or 2 companies having a large share of the market and able to charge over the odds thanks to their hold on the market.
On the other hand, you could argue that Govt is there to protect its citizens and ensure that businesses provide a fair deal to the citizens of a country. Great for the people, but companies see it as a less appealing environment in which to make money.
Generally, if one company is the sole provider of a service to individuals they know they can charge a high price and people will be forced to purchase their product anyway. Equally, when there are many providers but only one consumer, the consumer often has the power to haggle down the price. Of course, if the dominant party is incompetent, this logic doesn't always hold. When there are many providers and purchasers of a service, one tends to find nobody has dominant power, but that companies are forced to be efficient, consumers pay a fair price and everyone gets a reasonably good deal.
Govt seems to think that BAA was abusing its dominant position in London and Scottish airports by charging high fees for poor service and reducing what could reasonably be expected by the public. Until Govt enforces a separation of subsidiaries of a company and one waits a couple of years, it's difficult to know whether the Govt intervention has any benefit.