I am not an accountant, and I stand to be corrected if I'm way off on this, but I believe the GST system works this way.How so? Could you explain further? What do you mean by inputs?
A business collects GST on all it's sales, subtracts the GST paid on all its inputs to make those sales (In VIA's case Diesel, cleaning supplies, food and beverage sold onboard etc) and pays the government the net amount. If a business did not collect GST, then costs on inputs would be higher without the negating GST collected.
In other words, GST is paid by the final customer not each time along the procurement line.