Nope, neither. The owners simply didn’t want the tree felled, despite being told it was in trouble. (Ash dieback, AIUI).
For clarity, NR surveys trees within and outside the boundary that can affect the line. Where the tree poses a potential risk due to it’s health and/or position, then if it is in the boundary it will be removed. If it is outside the fence then the neighbour is contacted, advising them of their responsibility and liability. (I’m sure that as taxpayers, you wouldn’t want to be on the hook for the bill of tree management for every lineside neighbour). If it gets to the point of an immediate safety issue, then (usually) emergency arrangements are invoked.
However, occasionally, a tree that has been assessed as needing attention but is not an immediate safety issue can become one in a rather short space of time.
I guess the difference being made is that the "local distribution company" (which I am not sure is the same as your energy provider) will come and pay for it if required. If it's the infrastructure provider, and its nationalised, then it's ultimately the taxpayer. But I suppose Network Rail won't do the same is the argument being made.
So of course some people would rather just say "nope" and let it be somebody else's problem. And it appears that Network Rail then have to go through the local council to ensure action is taken. All of this will no doubt take a bit of time.