"Trolleyology": When is it ok to kill?

Trolleyology seems to be the name for a new branch of moral philosophy. Yes, a trolley is a train or something that runs on tracks (like a streetcar). You`ll find a very interesting article on the subject in http://www.prospectmagazine.co.uk/2010/ ... y-problem/, which starts with the following hypothetical scenario:

"A shocking memo leaked to Prospect [magazine], drafted by civil servants from the treasury and the department of health, exposes the stark reality of future cutbacks. Harsh decisions are inevitable, says the memo; in one NHS trust [,] people on life-support systems are to be “finished off” on 1st November—either by smothering, or by having the plugs pulled out. Their organs are then to be used to save the lives of others on transplant-waiting lists, who have themselves become a considerable burden to the taxpayer. The total saving to the trust is estimated at £2.3m a year."

NOTE: NHS trust = in Britain, a public health corporation that provides health care of one kind or another. I put a comma there [,] to help with the meaning.

But it doesn't sound to me any different from the dilemma I heard a long time ago:

You`re still young and strong, but in a sinking lifeboat with your mother, your spouse, and your child. You can save only one of them. Which one would you save?

Or is there a difference?