At this moment, it is not at all clear what this will mean as a result and how exactly the sanctions will affect business with the Russian carrier.
The EU document directly states, "It is prohibited to buy, sell, provide investment services or assist in the issuance of transferable securities and money market instruments, directly or indirectly..."
Page 135 then lists the companies affected by this provision, including Russian Railways. A similar provision on the US Treasury website
So, at the moment, this applies to securities trading and direct investment. However, it can be expected that further clarifications will be made over time.
What is probably inevitable, however, is that activities related to the rail link between Asia and Europe via the so-called New Silk Road will come to a halt.