There's something to be said for having neutral umpires as in international sport, but I don't know how that would be workable. I couldn't tell you the origin or favoured team of any umpire.
In any case, unconscious biases cancel out in the end, as Cobbler says - there are enough on-field, boundary, and goal umpires that to suggest the entire umpiring squad is in cahoots is ludicrous. If there ever were a conspiracy to favour a side, it would get exposed pretty damn quickly. In any case, cheating and throwing results in sport in general seems to be perpetrated predominantly by players (think of how many cricket cheats you can name who are players versus umpires).
PS On this topic, the controversial deliberate rushed behind in the Sydney vs Doggies game? If you're going to be strict on deliberates, that one is a free any day of the week. The outrage over that is a joke.