Taking nearly a year is just nonsense.
Let's take a hypothetical case - the train has a design fault. Nobody knows this yet. We're then going to dawdle through an investigation which should quite simple and straightforward, and eventually come up with an answer - this is if the badly-designed train doesn't kill a few people in the meantime.
It's now 16 days since the incident. Any evidence from the site; measurements, objects etc should have been completed days ago.
That leaves the now safely stored train. How long to inspect it? One week? Two perhaps? What's left to do?
I've heard of high-powered public service inertia but this is ridiculous.
If the ATSB or OTSI identify an issue as part of their investigation, they notify any relevant parties as soon as practicable.
Consider the recent Acroduster inflight failure up Brisbane way. Happened on the 18th August, they identified fatigue cracking on critical wing hardware on the 20th August, they've already notified the owner of the (only) other Acroduster on the Australian register, CASA & the NTSB, they've published a Safety Advisory Notice about the fatigue cracking and we have the Preliminary Report out on the 3rd November. And this is for a single-seat light sport plane.
They don't wait until the final report is ready before saying "Hey guys, we found this out 2 years ago, but didna tell anyone because we wanted the report ready".
However, I'm surprised to hear the ATSB or OTSI are looking into it, blind freddy can tell you what happened was both an intentional and criminal act, so there's not much to be gained from it, beyond maybe a recommendation about improved corridor fencing or better deterrents to stop vehicles leaving the crossing panels...Look at the datalog, confirm the Driver wasn't speeding, a quick review of sighting distances vs train location vs brake application and that's all that need be looked at, unless they want to get into systemic things like emergency egress....