Mmmh sorry but I have to disagree with you. I can't let you tell this without some corrections, non-expert people could take it as it is.
In short, your post is mainly uninformative.
>> Normally, these are sent to the client separately and merged in the graphics card
It means nothing. You moreover can't really know what the batching and draw calls scheme is in google earth nor in this nokia 3D maps.
>> Special routines are used to draw trees (e.g. billboards).
Mmmh. Ok ok. 3d applications are complicated, there is special routines for a lot of things btw...
>> What Nokia have done here is to merge everything - terrain, surface image, buildings and trees - into the same model.
I agree with that.. vulgarly. It does not mean there is one mesh and it isn't. It can be confusing.
What you mean is there is one skin.
>> They're still using the classic chunked level of detail approach, just with more complex models, which the graphics card handles with ease.
You don't know what the chunks and lod algorithm is and i guess it might be very innovative. Or not. Well but you are talking about the global chunked lod approach so you re right, but it can be very confusing. The LOD algorithm is probably very innovative.
>> This requires more work on the server side to prepare the data, but once it is done it is really fast for the client. The main disadvantage is that the data ends up being very static - you can't move objects around, for example.
This is just false. Please don't take it bad, people may be deceived by that and this is as false as possible. There is actually no benefit to explain why but it could looks like "there isn't any more server side preparation because the mesh is not construct on the fly, this is not faster in the client - you can't say it - it depends highly on the draw calls scheme, the vertex complexity, the textures fetches etc. etc. and the data are static you are right but yeah it is highly doubtful - 3D programmers are smart, take the example of moving BSPs in the quake engine, who could have say that BSPs can move...".
Anyway, thank you very much for the links and references, they are pretty interresting.
edit: please note that I'm trying to do all the efforts to make this post as constructive as possible.