There is no good explanation why Bastila and Revan, the most important people for the republic were alone near Taris. I agree that may be the ship was traveling to Dantoine in order to restore Revan's power. The sith new about Bastila and decided to trap her. (nothing about Revan, we know Malak was thinkihn he/she is death). There is a technical problem - the travel to Dantoine is in hyperspace, so sith may had used some interceptor field (like Leviatan on EbonHawk) in order to "extract" EndarSpire from hyperspace. But also a mathematical problem arises: the probability of a travel from one planet to another (Dantoine) to intersect some in-between planet (Taris), taking into account the space "size" is zero. Which means that EndarSpire was near Taris out of hiperspace on its own will to do something. Which again doesn't make sence ...