Yes, both of these seem to be 3d models rendered in real-time. If they were pre-rendered or hand-drawn 2d textures, then it wouldn't be possible to see the cannons from different angles while the camera moves. And if the house was just a static background texture, then it wouldn't be possible to cast dynamic perspective shadows onto it.
Objects which are so far in the background that the perspective doesn't change and that they do not have any light or shadow interactions with dynamic objects might be pre-rendered. For example, the wooden mast in the center of this section seems to be a pre-rendered 2d object. But it's hard to tell from video alone what background details are actual geometry and what details are just painted onto flat textures.
In general, the further something is away, the less it moves and the less light/shadow interactions you have with it, the more cheating you can get away with.