[Ward]

Lets assume we drop one (1) pop of a different race on a planet and

1) The new population now exceeds the planet's limit (which was reduced).
2) The number of facilities now exceeds the planet's limit.
3) The amount in cargo now exceeds the cargo limit.

What happens on the next turn?

I am guessing, but would think the excess population and cargo would be lost. But not the extra facilities.

You could have noticed that when you capture a planet with many troops your storage is overoaded(1000 kt of 200 kt). This happends to me quite often.