Last night I watched the first episode of the HBO miniseries referenced in the article having googled it and found it on Foxtel On demand.
In the first episode residents watched the reactor fire of a strange colour from the "railway bridge" as yet identified.
SO I asked myself has rail been used to deliver construction materials to the plant to build the new containment roof over a period of 8 years?
Chernobyl nuclear disaster site tourism: Visitor numbers surge after hit HBO TV series
When I went there in 2013, the rails looked like they may see very irregular use. The abandoned railway yard and rollingstock was interesting.
The new roof isn't that big and was longtime in construction. Note sure a train would have been needed.
What the train is more likely to be used for is the deconstruction of the entire power station site aside from Reactor 4 as its all now closed as of a few years ago.
EDIT: may answer some questions on its use.https://en.wikipedia.org/wiki/Chernihiv%E2%80%93Ovruch_railway