Are banned Pokemon in OU allowed in Ubers?

Question

For example, Sand Rush Garchomp or Soul Dew Lati@s.

Answer 1

Everything that is not covered by a metagame-wide clause is allowed in
the Uber tier.

According to the rules in the source, your two chosen examples are allowed as well as Drizzle+Swift Swim combination and Snow Cloak ability.

Source: http://www.smogon.com/bw/banlist/

Note: These are Smogon's rules for Generation 5, so with the advent of Generation 6, things may change (like Drizzle and Swift Swim may become legal due to the weather nerf.)

Answer 2

Yes. Unless it's a hackmon.