Hot times ahead

According to Bulgarian State Railways…

On 25 October, “Bulgarian State Railways” EAD started heating all categories of passenger trains. In accordance with regulatory basis, train heating should be turned on as of 1st November.

It would be too easy to infer from this story that it is usual that only some categories of passenger trains would normally be heated, but since I have never quoted a story from Bulgarian railways I am going to give them the benefit of doubt.