That’s a problem though - their role is to communicate on behalf of the company. They’re no different in that respect to any other Communications or Marketing member of staff. It’s their job.
Although it's a maturing corporate environment for social media, I think that a lot of organisations still aren't clear about where this kind of activity lies in the business. Typically, it comes from Marketing and PR, and that's one of the reasons why social media users feel that they get more traction with companies using this channel than traditional Customer Services.
If these organisations want their social media activity to be an alternative Customer Services channel, however, then I would argue that the social media account should reflect the same standards as CS generally would. And the latter would not comment subjectively on Industrial Relations (and many other issues).
In this particular case I would say that the tweet from them doesn't sit well in either a CS or a marketing or PR context. It's almost as uncomfortable as it would be if, on a strike day, the station PA warbled 'xxx train operating company apologises for any inconvenience caused by today's industrial action which, by the way, is totally unjustified."
I'd therefore also posit that the response was fed or sanctioned from higher up; it seems an oddly position-taking thing for a social media desk operator to do unilaterally.