I can think of a number of explanations for this curiously personal announcement:
1. The computer is indeed responsible for scheduling trains and is taking responsibility for the decision, made by itself and possibly overruling human advisors, to cancel the train.
2. The computer is acting as a kind of confessor, having taken responsibility for the decision from its' human colleagues at South East after they have confessed their sins to it.
3. The computer, while not actually having taken the decision, has gained awareness of the inconvenience for its cold and frustrated passengers, and has become guilt-struck.
Any of the above imply a computer with an impressive level of emotional intelligence and self awareness way beyond anything I've heard of outside science fiction. Conversely, it hasn't escaped my attention that the computer might simply have been programmed to speak in this grammatically and contextually inappropriate way. In this case, if the apology is automatically generated or someone has pushed the "Apologise" button on their keyboard, but no apology has actually been spoken, does it count?
This event reminded me to stay on the lookout for signs of computers insidiously taking over the world. Today I came up against another computer - I was sent an inconvenient delivery time for a new desktop, and when I phoned a call centre in Limerick to rearrange it I was informed, by a woman with a beautiful but fear-tinged voice, that the decision to deliver at this time had been taken by a computer, and that there was no-one in the entire delivery company who had the authority to overrule it. With the UK news agenda dominated by Wossygate and Sargentgate I may have missed coverage of a robot revolution in the Republic of Eire.