No.
Firstly, a TIR is not a Witness Statement.
But if I read your question as if to refer to a Witness Statement (referred to by the Police and by Revenue staff in the rail indstry as an
MG11), then yes, it MAY be used as the sole item of evidence in Court.
However, I think it unlikely.
I would expect to see further Statements from the staff involved in obtaining the Statement, perhaps 2 or 3 would be required in addition to the Passenger's Statement, all dependant on the circumstances and version of events provided (eg from the officer who detected the irregularity, such as a Gateline Inspector, from the officer at the boarding station such as a Ticket Office Clerk and perhaps a Revenue Witness present at the Gateline. In some cases, a Statement from the guard could be necessary).
With such a bundle of sworn Statements, an uncontested prosecution should have a reasonable prospect of success.
If it was to be contested, then some of these Statements may be replaced by oral evidence and perhaps the Defendant would have their own Witnesses.
A grovelling apology here and admission of guilt hands the TOC the evidence they need to prosecute.
Well if we're not going round in circles, then we're getting stuck in a rut. The matter of Evidence of Guilt in a Strict Liability matter has been dealt with in several posts. I shall not repeat it.
I have discussed Judgements of Claim Dismissed (effectively Not Guilty) in strict liability matters previously, but they are highly exceptional, and it is unlikely that a Prosecutor would advance a Claim without confidence that the Evidence was adequate. If the Evidence is inadquate and the Defendant's representative proposed contesting the Claim, I would expect the Prosecution to withdraw the Claim without wasting further time (unless there were exceptional circumstances).
All I can add is that a professional relationship tends to become established between Criminal Defence Lawyers and their local CPS team, which does allow for a lot of frank and pragmatic discussion to take place which in turn reduces the number of unproductive cases taken to the Courts. As I've already discussed in this thread, the lack of Law Firms with specialist Railway Ticketing experience has led to the lack of such constructive discussion with professional colleagues before a Prosecution, and so a High Street Solicitor may be on unfamiliar ground calling a Railway Prosecutor for the first time - perhaps this had led to more cases being advanced for Prosecution than might occur if the CPS were appointed to process Prosecutions, but I doubt it has been significant. The greater hazard is that the Defence Solicitor simply assumes that Railway legislation is more similar to other Crimial or Traffic cases than is helpful to assume.