I would not be wanting to try and do a lot of maintenance on a clapped out tank that had just been driven hundreds of miles to Emu Field - there’s a reason they set off nuclear bombs there - because it was in the middle of nowhere with absolutely nothing of value to be damaged. The nearest road (and that is an unmade dirt road) is 120 miles away. The nearest human settlement (a town of 2000 people, most of whom live underground because of the heat) is 150 miles away. And that town is 500 miles away from the nearest city.
Just for fun, I’ve just used my navigation software to tell me how I should drive from where this tank was (Puckapunyal Army Base in Victoria) to that nearest town to the nuclear test. It’s about a 1000 mile drive, and could be done nowadays - nearly 50 years later when we have much better roads - in about 18 hours in a car. Even if the tank could match that all the way without breaking down, figure at least 21 hours to get to the test site, and if you need four hours of maintenance for every hour you drove - 84 hours maintenance. I’d say it was just a lot easier to transport it the way they did it, and a lot less labor intensive in the end.
Train shipment makes sense and sounds fine. I had to laugh about the stretches where the tank had to be unloaded and used to pull the transport. Since that tank was set to be scrap, I’d driven it in by itself (as a durability test).