In the January 1805 start, Hannover is free and not occupied by France.
However, according to the first source I could find (Wikipedia), Hannover was occupied since 1803. The Convention of Artlenburg was the official surrender of Hannover, and the French only withdrew in Autumn 1805 to fight the Austrians. The odd thing is that in the August 1805 scenario, France DOES occupy Hannover. This seems to mean that the developers are aware of the French occupation of Hannover, which is great.
Just wanted to point out this weird little situation, and I hope it is fixed as soon as possible. There are a lot of fun and interesting events that could be done with Hannover, Prussia and France too.
Enjoying the game so far, thanks for all the hard work and looking forward to the first patch coming out!