Vendor lock in by rolling stock manufactures
  Matthew Geier

It's not directly 'trams down under', but we buy equipment from
manufactures who MAY indulge in this behavior.

Basically NEWAG (Polish rolling stock manufacturer, I think they have
trams/light rail products too), coded logic bombs into the train
computers - if a train spent too much time at a 'competitors' workshop,
the train computer disabled itself. And it was viral - the railway sent
a train to tow one of the disabled trains out, only to have the rescue
train disable itself when coupled to the broken one.

The article is for techno geeks and translated from Polish, but
basically the OEM maintenance contract on the new(ish) trains expired
and another company won the contract. They took train in for it's
regular programmed maintenance, did exactly what the manuals said, but
the train would not power up afterwards. After several disabled trains
and OEM claiming the maintenance provider just didn't do it properly,
the railway hired some 'hackers' who 'de-compiled' the train computer code.

What they found in that code should be illegal if it isn't already. It's
even worse than VW cheating on emissions testing. These trains disabled
them selves if they spent too much time in a competitors workshop and
had calendar based 'failures', where it would report a subsystem failed
on a certain date regardless of the actual subsystem operational status.

I'm sure other manufactures do this crap too, NEWAG just got caught out.