Google tells me that Germany has seven freight train services a week going to/from China.
http://tbngroup.de/en/internation-forwarding-logistics-from-...
That's just ~28 km/h on average. I ride my bicycle faster than that :).
[1] A bit old but fairly indicative as far as I can tell: https://www.rita.dot.gov/bts/sites/rita.dot.gov.bts/files/pu...
However, this article says:
"The exit customs inspection for the Su’Man’Ou trains is done on-location in the bonded zone. The next time these containers will need to go undergo a customs inspection will be at the border of the EU, and they will typically not be opened until they arrive at their destination."
and
"These cargo relays are generally very simple procedures: the incoming train and the outgoing train are lined up side by side and a crane moves the containers from one to the other. At Khorgos Gateway, a new junction on the Silk Road Economic Belt on the border of Kazakhstan and China, this transfer can be done in just 47 minutes."
15 days is half a month. But if this could be shortened to 10 days, it is 3 regular shipment in a month.
For someone like Apple, this could be extremely cost efficient. Rather then paying the high price to book every single possible fright from China, they could now do it via train, at least to everywhere in Europe.