Alive has posted only twice. This was his first post, and his second post, three minutes later, was to the Civ 4 section. So there's a good chance this post was also meant for the Civ 4 section. The same goes for you Herrhals.
Of course, if you & he should return and confirm that he's playing Civ Rev and clarify his question, I'm sure we will provide an answer.
But, for your question. In Civ Rev, there is no additional benefit to working multiple terrain bonuses beyond the bonuses themselves. I've seen this with island cities having access to multiple fish tiles. Each fish tile worked provides 2 food on top of the 2 trade provided by the sea tile.