sorry to hear about you having to work weekends... no fun. ever. :) the quest in question (lol) is called "stables" and yes it does sort of control the players horses, but only up to a point it seems. it gives the horse selling guys some dialogue, controls how much you pay for em, etc... I have tried to stop that quest, reset it (which set all the Aliases to none), cleared just the "PlayersHorse" alias on that quest, none of that had any effect, my horse still fast traveled with me. I actually made a little mod with an item I can use to test manipulating that particular quest, unfortunately none of my ideas worked. I too looked at the source of many of the vanilla scripts to see if there was something "hidden" in there, there wasn't, as you found out. We might be just jumping at shadows here... but I hope not, it would be very handy to be able to drop off a horse somewhere and be able to fast travel without them.