There actually is a (Conventional, sleeper) train between Moscow and Beijing - the Vostok (East). If you transfer from the Moscow-Berlin train, the "Swift", you can theoretically make a train-only journey from most of Western Europe to China.
Report: Chinese trains departed for Europe mostly empty
http://trn.trains.com/news/news-wire/20 ... stly-empty
The linked article.
https://www.inkstonenews.com/business/w ... le/3023705
Whilst this doesn't provide any proof, it doesn't take to much imagination to believe this was happening. OTOH, I doubt they would have trouble filling an empty container, even if they charged sea rates, they would make more than sending it empty and claiming the subsidy alone.
The current rate of empties seems normal for any service, so perhaps it has been worked out.
