Should the government provide subsidies for the development of high-speed rail networks?

Yes, but only if there is a proper financial and construction plan.

Not unless there’s a clear path and financial plan.

Yes, but FFS learn from oversaes practice. HSR only works where it replaces an existing air corridor, as its usually the same price or less, better resourced, easier to access and probably more comfortable.
So Sydney to Newcastle is a total dud.
Sydney to Melbourne via Canberra would be cheaper and actually make money.
The key is to get freight onto the HSR and so compete with road transport, as freight is where the money is. But rail freight works best for bulk cargoes or longer distances, as it gets cheaper the further you haul it. The opposite of the argument for passenger HSR.
But definitely, Sydney - Newcastle is NOT the one to choose for the first HSR in Australia! Too expensive, not enough patronage (as it will be too expensive and too hard to access) and doesn't replace an air corridor.

No, because the government should be developing a national high-speed rail for the public, not throwing money at private corporations to use it for their own benefits.

No, unless there is a clear plan on how to go forward with it, and it attracts a lot of users. Otherwise, it is just a waste of money.

Yes, these should go to private companies who compete to build the best networks possible.

Yes, but rail networks should be nationalized to ensure fair and affordable access for all Australians.