Currently FSN can be found on 576/76 (HD/SD). A number of events (notably Dallas Stars Hockey Games - 12 this season) are pushed to FSN+ due to programming conflicts. This is a supplemental channel that FSN uses.
I don't know if other FIOS TV markets have FSN+ (seems like I've read they do). How do (Can) we get it here in Dallas?
Time Warner, Dish, DirecTV all carry it.