Well there sort of is with Building hexes. I know it doesn't say they can occupy only part of the terrain in Bridge hexes but it doesn't say they can't either that's where our confusion came from.
Yes, that's the case with building hexes, because it specifically states that case. I've mentioned before that the rules are very specific and that if it isn't stated that it applies or it doesn't apply, that's it. One situation doesn't translate to another situation. If that were the case for bridge hexes, it would be stated just as is the case for building hexes.