Can spots be reserved at Fishing Bridge RV Park Yellowstone?

Actually, the Yellowstone reservations crew do operate from Yellowstone, not Denver, so some of them (probably many) have actually been to the CG. That said, it's quite large, so they probably don't have the exact layout, size & alignment of each campsite in their heads - that would take a savant! As others have said, they'll do the best they can, but can't guarantee a specific site.