Fertilisation can take as long as 6 days so the morning after pill, can stop ovulation, or the implantation of the fertilised egg, in the same way as an ordinary birth control pill or a coil.
Roman Catholics would object as they do to birth control, but it wouldn't be classed as an abortion for...
Slightly off topic, but why aren't women automatically given the morning after pill, when reporting a rape? Having said that, stranger rape is rare, as it's more likely to be 'date' rape, and the woman doesn't always report it straightaway.