I have a MS in Nutrition and have done some research in this area, so while Im no 'expert', I'll share what I know.
Women take EPO because it is a source of gamma linolenic acid (GLA) which is a precursor required for the synthesis of the prostaglandins that soften the cervix in labor. However, most people are not deficient in GLA if they have a well balanced diet. Also, in the case of shortage, GLA can be manufactured in the body from linoleic acid, which is typically abundant in most diets. So, for most healthy women, taking EPO shouldn't REALLY have an effect on cervix ripening. However, as with many things, science can't explain everything, so if women anecdotally think that it has helped them, perhaps it has.
Also, it should not matter whether the EPO is taken orally or vaginally. It would definitely not have an 'opposite' effect depending on method of ingestion. I would think there is probably a better chance of absorption through the intestinal wall, rather than the vaginal wall.
Mommy to DS1 5/07 and DS2 1/09 , wife to an awesome hubby. And someone new coming in March!