The hut and special patterns are always the same though, regardless of what the map is like, but remember that you never get specials on grassland and you never get huts in the water.
Not exactly

.
The hut pattern is fixed, in relation to the patter on
placement of specials. However, the pattern of specials, and the location on a given map, depends only on one thing.... the initial seed value. If you choose a seed value of, say, 17 (use map editor), then that sets the mixure and patters of whales/fishes. There are 2 categories of patterns, BTW.... I call them whales and fishes, since in a 100% ocean terrain, that is how they "start out". As you change the underlying terrain, the special that will result is ordained. For example, a whale will always become a wine, if the ocean is changed to hills. Fish will always become coal. I like wine. I like whales. (so the moral is that whales are my favorite specials category, LOL

).
Specials come in groups of 8, and the mixture of whales/fishes within that group is determined by the seed value and does not vary, once the seed is set. It repeats again and again, until the map (whatever size) is covered.
The way it repeats is this: take the 8-special pattern, "copy" it, and paste it again and again horizontally, with a 3-diagonal tile spacing.
On the next "row" (horizontal pattern), "flip" in about the horizontal axis.
but remember that you never get specials on grassland
I think you're saying that you just can't "see" it in grassland. You can indeed have a grassland special -- but grassland does not get any extra bonus or outwardly visible indication that it is special. Mining or transformations will reveal the appropriate special.
Once one determines the special layout in a map, you can predict the location of every special on the map, and every hut on the map. We are going to do just that in our Democracy game, BTW

. That hut is very telling, as soon as we verify a special or two, hehe.